These days, you have to be careful not to slip as you walk across the parking garage at the 55/65 Harbour Square condo building.

Water from Lake Ontario has been seeping into the downtown building's single-level concrete parking garage of the downtown building and algae is starting to grow in some of the flooded areas. The only things that have been parked down here for a few weeks are the industrial pumps that have been running around the clock.

"We're pumping close to 1,800 to 2,000 gallons of water per minute, every day," said Ivan Caballero, the condo's maintenance manager. In his 11 years working at the condo, he has never seen the parking garage of the 40-year-old building flooded as it is right now. It's one of 15 buildings that the city's Toronto Water division says have been affected by rising water levels in Lake Ontario.

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Spokesperson Ellen Leesti says in total 10 condos, two houses and three commercial properties have reported issues in the city because of the swelling lake that has closed the popular Toronto Islands and eaten away at the city's beaches.

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According to Environment Canada, the Toronto region recorded 142.6 millimetres of rain in May. Environment Canada's senior water resources engineer, Jacob Bruxer, said Lake Ontario's levels are at the highest they've been since 1993. In some areas, the lake is more than 0.5 metres higher than average. The average depth of Lake Ontario for May was 75.80 metres. The latest measurement for June is 75.86 metres.

It was five weeks ago when Mr. Caballero noticed water coming up from under the concrete and filling the visitor parking area of his building. Built near the bottom of York Street, the condo has about 2,000 residents split between 600 units over 30-plus storeys. The building has only a single level of parking that is semi-underground.

"It's been quite a challenge and we are just praying it goes down," Mr. Caballero said, adding that the main goal has been to keep the water away from an electrical-supply unit in the area.

"That has been our priority to keep the water levels down because that is a [potential] explosion that could shut down different buildings down here."

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Toronto Hydro spokeswoman, Tori Gass, says all electrical supply infrastructure at the building was "dry for now." Crews have been inspecting electrical equipment in the area all week. "We'll continue to inspect these locations until the water levels have subsided," she said.

Mr. Caballero said cleanup and pumping rentals have cost about $30,000, which is unlikely to be covered by insurance. Ms. Leesti said she wasn't aware of any municipal funding that could be available to help offset any costs attributed to flood damage.

Engineers were brought in and drilled a hole into the concrete to test the ground's makeup underneath 55/65 Harbour Square to determine how much erosion and washout have taken place. Mr. Caballero says engineers have indicated the building is still "structurally sound."

"Now, we are more in control," he said. "It is still quite a troublesome situation to keep it in good condition."

The condo building next door is also experiencing flooding in its multilevel parking garage.

"We've had two occasions in the last two weeks where we have been affected by flooding," building manager Laura Lee said. Water pressure from Lake Ontario is affecting the city's sewer system, causing backups that burst a pipe in the parking garage. It has already cost $35,000 to clean up.

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"It recedes and then with the rain it comes back up … hopefully, with the sunshine some water will evaporate and the lake will go down," Ms. Lee said.