Protecting Pflugerville’s water supply from zebra mussels will combine short- and long-term solutions that will begin soon.
Council members voted to approve more than $51,000 in funds as the first step to combat the invasive species, found on a pump last fall in the intake tower at Lake Pflugerville. Officials said the water is piped in from the Colorado River and there is no immediate issue with the city's water supply.
"There isn't a danger," Pflugerville Assistant Manager Trey Fletcher said. "We have been evaluating this for some time and we needed to come back with an appropriate way to manage this and cope with it forever. This is the first move."
Fletcher said the goal is to protect Lake Pflugerville for its "core intended purpose as a water source without sacrificing recreation [at the lake]."
The mussels can clog pipes and screens, damaging infrastructure and equipment and slow water treatment if left unchecked. Zebra mussels have not been discovered in the lake, but it is only a matter of time, according to Darren Strozewski, principal at DCS Engineering in Austin.
“They are going to be part of our lives forever, until somebody comes up with a silver bullet,” Strozewski said.
Strozewski and DCS Project Engineer Jessica Simpson presented information to the city council at a work session before Tuesday’s council meeting. Council members followed with unanimous approval of $51,738 to clean the raw water intake which has 90 percent of zebra mussel growth on the bottom half of the pipe. The contractor, Underwater Construction Corporation, will remove debris and mussels from the entire system, spelled out in a multi-page bid here.
An issue in the Great Lakes since the 1980s, zebra mussels made their way to Texas, recently causing an odor in drinking water in South Austin’s water supply. Cedar Park and Leander have addressed the mussels at recent meetings and the first area sightings came in Lake Travis in June 2017.
Strozewski and Simpson offered short-term solutions that include installing a permanent sodium permanganate dosing system at the Colorado River intake pumping station and the Lake Pflugerville intake tower, pumping station and transmission line, and using divers to keep track of zebra mussel numbers in the intake pipes.
Long-term solutions recommended were installing the dosing station, continuing to stock the lake with carp, removing debris and banning boats with gas operated motors.
While the use of gas motors is currently banned, boat motors are means of spreading zebra mussels. They attach themselves to intakes and hard-to-reach places, Strozewski said. It is one way they have traveled from the Great Lakes region to the south.
One of the long-term solutions, when the infestation is more prevalent in the lake, is to lower the lake 14 feet from its current level for a month. Strozewski said the lower level would drive the zebra mussels into deeper water to maintain their food source and help eliminate them from washing up along the shore or on to the beach. The mussels, which have razor-sharp shells, live up to two weeks without food.
Strozewski said the average depth of the lake is 17 feet, while the level at the intake tower is 34 feet. The water lowered in February is off-season, while peak usage is June through August. Strozewski said while it is one option, it may not be popular to have the lake lowered, even during the winter months.
Another long-term option, with a capital expense estimated in the range of $1 million, includes a pretreatment system installed at the water treatment plant. That solution would bypass the current system and would likely come as the city neared build-out, estimated to be 250,000 residents, according to officials.
After the meeting, Council Member Rudy Metayer said the council's No. 1 goal is protecting the drinking water for the residents of Pflugerville.
Fletcher said the city will work with the experts to develop the timeline and future options moving forward.