The City of Winnipeg is taking preventative measures to deal with an "inevitable" zebra mussel invasion of the source of its drinking water.

To date, no zebra mussels have been found in Shoal Lake, which straddles the Manitoba-Ontario border. But Winnipeg water and waste officials believe it's only a matter of time before the invasive species makes its way into the Rainy Lake/Lake of the Woods watershed, which includes Shoal Lake.​

The mussels, already present in both the Great Lakes to the east and the Red River/Lake Winnipeg drainage basin to the west, are capable of coating metal surfaces and clogging drainage pipes.

Winnipeg has $1 million set aside to protect the Winnipeg Aqueduct intake pipe and other aspects of its intake facility at Indian Bay on Shoal Lake, water and waste engineering manager Geoff Patton told city council's environment committee on Thursday.

"They can attach themselves to several metal structures or other concrete structures. They build up a significant mass as they begin to cling together and that can actually cause restrictions in the flow of water from the lake into our intake facility, and therefore limit the water to the City of Winnipeg," Patton told reporters following the meeting.

The zebra-mussel project should be completed by 2019, Patton said. It's part of $9-million worth of improvements planned for the Winnipeg Aqueduct intake facility over six years.

The city intends to use chlorine to kill adult zebra mussels and the worm-like, free-swimming mollusc larvae known as veligers.

Patton said there are no plans to conduct zebra-mussel inspections on boats carried by vehicles that will use the forthcoming Freedom Road, which will connect the Trans-Canada Highway in Manitoba to Shoal Lake 40 First Nation, which sits on a peninsula that divides Indian Bay and Snowshoe Bay.

That peninsula was cut off from the mainland in 1915, when a channel was built to divert the naturally murky outflow from Falcon River away from Indian Bay and into Snowshoe Bay.

Construction on the 24-kilometre road began in 2017 and the on-reserve part is complete. It is expected to facilitate the construction of a water-treatment plant at the Indigenous community, which relies on bottled water shipped in by ice road or by ferry.

Patton said the city may use this road to service its intake facility to some extent, but must continue to operate the Greater Winnipeg Water District railway to maintain and repair the gravity-powered, century-old Winnipeg Aqueduct, much of which is inaccessible by road.