Divers have found large amounts of invasive zebra mussels at intake pipes that feed Austin’s water supply, opening up a costly new challenge for the city’s water utility.
Austin Water had seen evidence of the small, rectangular mussels in water samples and around intake pipes earlier this summer, but that was nothing compared to what they found when they sent divers down to take a closer look this month.
Mehrdad Morabbi, an operations manager for Austin Water, says one of the screens protecting the intake pipe for the Handcox Water Treatment Plant in Lake Travis was 50 percent covered with mussels, another was around 30 percent covered. For reference, these screens are 24-feet-tall and 30 feet in diameter. Divers removed the mussels from the screens with a pressure washer.
Morabbi says there’s evidence of the mussels at intake pipes for Austin’s other two main water treatment plants, but Handox is likely the first to see major infestation because it’s upstream from the mussel infestation in Lake Travis.
“As we do more and more inspections and cleanup then we’re going to be able to gauge the level of growth and then we’re going to be able to set up the number of frequencies that we need to do for cleanup,” he said.
The city is working on a plan to use chemical treatments to fend the mussels off. Austin Water hopes to have recommendations for that plan from a consultant within a month. After that, it will need approval from the Texas Commission on Environmental Quality to proceed.
“Obviously we can’t start injecting chemicals into the lake, so at some point there’s going to be a line in the sand that we just can’t cross [with chemicals] and then anything beyond that line will have to be done manually,” said Morabbi.
However, other cities with zebra mussel populations have found controlling them to be expensive. Morabbi says he’s not sure what they might ultimately cost Austin, but the contract for the divers to inspect and clean infrastructure runs around $212,000 a year.