Austin City Council has approved spending up to $4 million over the next five years on a liquid compound to remove zebra mussels from water intake systems.

Zebra mussels are small invasive mollusks that can clog the pipes that pull water from reservoirs. Austin gets its water from Lake Austin and Lake Travis, both of which are infested with zebra mussels.

“They reproduce quickly and can start to line entire segments of a pipe and then eventually start to fill and close off the pipe itself,” says Liz Johnston, environmental program coordinator for the city’s Watershed Protection Department.

The chemical compound, known as EarthTec QZ, is liquid copper sulfate pentahydrate. The city says it’s registered with the U.S. Environmental Protection Agency as a way to control infestations of zebra mussels.

Johnston says copper sulfate can be fairly toxic to aquatic life, meaning it’s capable of killing zebra mussels and could harm other aquatic organisms as well. But the manufacturer says the level of copper sulfate in EarthTec QZ is lower than it is in other copper sulfate products.

“This particular product is labeled for use as a molluscicide, and so the dose is lower than what would be used for other products,” Johnston said.

The city is also working to retrofit water-intake structures to reduce the risk of the compound killing animals in the lakes.

“Because this chemical is going to be used at the intake — so very, very close to the lake — we’re working with them to make sure that it doesn't get into the lake,” Johnston said.

The city has $533,333 available to pay for the molluscicide in its current budget. Funding for the remaining term of the contract will be depend on what money is available, according to city documents.

Zebra mussels arrived in Lake Travis in the middle of 2017. Last year, the mussels' presence in a pipe led to smelly tap water; it took the city days to flush the system.

The mussels are often spread when people who boat in infested waters then enter clean lakes without properly cleaning their boats. Once they reached the Colorado River, the mussels have gradually moved downstream.

“There’s billions of larva out there at a given time that can later become adult zebra mussels,” Johnston said. “Not only do they attach to structures, but if they’re adult zebra mussels, they’ll attach to those zebra mussels and on and on.”

The mussels have fully infested 18 other Texas lakes, including Lake LBJ, Lake Marble Falls, Lake Pflugerville and Granger Lake.

Got a tip? Email Marisa Charpentier at mcharpentier@kut.org. Follow her @marisacharp.

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