Flooding caused by a cloudburst on Wednesday was the result blocked sewer grates. - NEWS PHOTO COLLIN GALLANT
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Flooding caused by a cloudburst on Wednesday was the result of above-ground conditions, specifically blocked sewer grates, rather than any shortfall in the storm sewer system, city officials have determined.
With more than one inch of rain falling on the south hill in Medicine Hat over about 90 minutes that night, residents saw a rerun of flooding that was common at intersections near Division Avenue Safeway more than a decade ago.
Those types of scenes – water above car hubcaps and even kids in kayaks – had mostly subsided when catch-basins were doubled in size 10 years ago.
But, they briefly returned Wednesday before city crews were dispatched and found inches-thick mats of seed pods and leaves blocking grates.
Once the grates were taken up “the water drained quite quickly,” said Jeremy Petryshyn, the city’s manager of city surface assets.
In 2013, the city spent $1 million to upgrade drainage vaults and storm sewer capacity on four roads that border the Moose Recreation Centre. That largely avoided repeating floods at nearby intersections in the low point of the community, said Petryshyn.
He said the problem this week was largely unavoidable and “basically comes down to the intensity of the rain and the stage of the trees.”
Of particular blame are seed pods from ash and other trees on the hill that remained on branches through the winter, or were deposited in household rain gutters.
“The rain was so hard that downspouts were basically going full bore,” said
“All that, as well as debris on lawns, was swept out into the street.”
The material gathered and blocked or slowed local drains, thereby sending more water generally downhill to Division Avenue, where drains also plugged.
On Friday, lawns near Sixth Street still had a ring of leaves denoting a high water mark two or more feet above the street drains.
City crews began roadway cleanup on Wednesday night and street sweepers were dispatched on Thursday and concluded work on Friday morning.
The city’s capital budget plan includes money to repave and add pathway to the length of Division Avenue on the South Hill, but engineers are still determining if drainage components may be added.
