The City of Winnipeg is concerned about the possibility of zebra mussels entering the city's water supply from Shoal Lake, so it is seeking proposals for a facility that it hopes will keep the invasive aquatic species out.

Officials are seeking proposals to build a copper-ion generating system at its Shoal Lake Aqueduct intake facility. Bids for the project close on Nov. 20.

According to its request for proposals document, the city says it can use "continuous chlorination" to control mussels in the short term.

However, chlorination is not a good long-term solution "due to concerns with the reliability of the existing system, regulatory requirements for disinfection by-products, staff safety, and potential for environmental impact from transporting large amounts of chlorine," officials say.

Zebra mussels have been found in the Red River in North Dakota as well as in Lake Winnipeg.

The small, filter-feeding mussels, which reproduce aggressively, were first spotted in the lake's algae-ridden waters in October 2013.

"The likelihood of their introduction into Shoal Lake has increased," according to the city's request for proposals.