If you were thinking about taking a dip in the lake at Toronto's Harbourfront area, you may want to make other plans.

Tuesday's heavy rainfall, which totalled about 70 mm within a 24-hour span, caused a large sewage spill into the city's Inner Harbour.

As a result, an excessive amount of condoms, pads and tampons was found floating amid the garbage.

"Anything that floats that people are flushing down their toilets, we're seeing," said Elise Mackie, Toronto community monitoring coordinator for Swim Drink Fish, a group that frequently tests three of the city's piers for E. coli and garbage.

Elise Mackie says she saw 'tampons, condoms, we actually saw toilet paper clumped up, feminine pads,' when she and her group assessed the water at three Lake Ontario piers following Tuesday's storm. (Gary Morton/CBC)

"In the immediate aftermath of that storm it was pretty gruesome down there."

Because Toronto has a combined sewage and storm-water system, heavy rainfall means excess amounts of sewage and storm-water have to be sent somewhere. In Toronto, that somewhere is Lake Ontario.

Swim Drink Fish is monitoring the spill, and they have a warning for all Ontarians: avoid contact with the water for the next couple of days to avoid exposure to bacteria and waterborne illnesses.

All locations tested for E. coli failed

Swim Drink Fish also tests the water twice weekly during the summer to track E. coli levels — the more of the bacteria found, the more sewage is present.

All the locations (Marina Four, Rees Street Slip and Bathurst Quay) that were tested Thursday failed, and had the highest bacteria levels the group says its seen in two years of monitoring Toronto's Inner Harbour.

The group follows the same standards as the City of Toronto. The city tracks E. coli levels daily, and is also alerting the public that heavy rains and high water levels in Lake Ontario may have created unsafe swimming conditions.

Those looking to swim or partake in water activities in the Harbourfront area should wait at least another 24 hours, according to the group Swim Drink Fish. (Gary Morton/CBC)

"They have all significantly surpassed the local standards," said Omid Razavi, communications manager for Swim Drink Fish.

Razavi said Marina Four, which is west of downtown, was the worst, surpassing standards by 249 times the amount considered passable.

"This is the worst that we have seen Marina Four to date," he said.

Bathurst Quay, across from Centre Island, failed 100 per cent of the times it's been tested this summer.

After heavy rainfall, like the one Toronto experienced this week, Mackie says garbage like microplastic and gloves are typically found.

Swim Drink Fish tests the water at three of Lake Ontario's piers twice a week during the summer months - Marina Four, which is to the east, maxed out the level that can be measured. (Gary Morton/CBC)

But the storm this week brought infrequent kinds of garbage into the water, another illustration of a bad year overall for pollution at these locations.

"It was something I hadn't seen yet this summer, and I'm hoping we don't see again," Mackie said.

The city says people shouldn't swim at all after storms or heavy rainfall in general, and that cloudy water could be an indicator of high levels of bacteria.

'Go and shower'

Although it's prohibited to swim in these marinas, people, especially children, are advised to go to the islands for any of their water activities.

If someone does come in contact with contaminated water, Mackie says the first thing they should do is: "Go and shower."

But with the work of her and her team, Mackie hopes one day people may be able to swim in these areas.

"Maybe one day we'll be able to come here and swim," she said. "That's kind of the goal here."