JOSHUA ALLAN
The 1510 West

West Islanders looking to beat the heat by taking a dip in Lake St. Louis, Rivière des Prairies or the Lake of Two Mountains may want to check the water quality before diving in. Data collected by Montreal’s aquatic monitoring network points out which shorelines are safe for swimming and others that residents should steer clear of this summer season.

Of the 45 points along the West Island shoreline where the water was tested by the Aquatic Environment Monitoring Network (RSMA) last week, eight were marked as being “poor” quality, while one — along the shore of the Parc de la Rive-Boisée in Pierrefonds-Roxboro —was listed as “polluted.” This data is made available through an interactive map on the City of Montreal’s website.

RSMA calculates the quality of the water based on the number of fecal coliforms — bacteria including E. coli, found in plant soil as well as human and animal feces — measured per 100 millimetres. Levels acceptable for swimming must not surpass 200 coliforms per 100 ml.

Areas measuring 1,001 or more fecal coliforms per 100 ml are listed as “polluted.” Swimming in polluted water can lead to gastrointestinal illness.

Last week, the water along the shore of the Parc de la Rive-Boisée was measured as having 10,000 coliforms per 100 ml. This is not unexpected, as data going back to 2012 shows that the water in that spot routinely scores high in fecal coliform due to a nearby storm sewer pipe draining into the river. Swimming is not authorized at the park.

Of all the areas tested, the waters behind Stewart Hall in Pointe Claire was measured as having the best water quality in the West Island, with just seven coliforms per 100 ml. The only shoreline in all of Montreal with better water quality was at the southern point of the Jean-Drapeau Park, at just two coliforms per 100 ml.

The longest stretch of waterfronts that were measured as having “good” or “excellent” quality water reached from Kelso Park in Ste. Anne de Bellevue all the way to Bayview Park in Pointe Claire.