Holmes Beach is going to turn Spring Lake upside down.
At their April 23 meeting, commissioners unanimously approved a motion to install an aeration system by Vertex Water Features of Pompano Beach in the brackish lake between 68th and 70th streets. The system will pump 7 million gallons of lake water with oxygen, allowing the entire lake, from bottom to surface, to turn over two times in 24 hours.
The lake, with 3 feet of muck accumulated at its bottom, recently underwent a review to determine the best form of cleanup.
At an April 9 commission meeting, Burnett said tests performed by Manatee County determined the bottom sludge mostly is algae, which digests pollutants. She said this is why prior water-quality testing indicated the lake is clean.
Previously, the city considered dredging the lake, but Burnett determined it would cost about $540,000 to dredge a foot of muck, versus less than $7,000 for the installation of the Vertex system, including water-quality testing and semiannual maintenance at $388 per year.
The aeration system will generate millions of small air bubbles, lifting bottom water to “turn over” and blend the salt- and freshwater to vent gases harmful to the lake, while allowing absorption of oxygen, according to a Nov. 7, 2018, email from Vertex sales manager Chris Byrne to Burnett.
Eram Wasserman, a project manager at Burnett’s firm, LTA Engineers, said the system comprises a compressor, valve box, tubing and four diffusers.
He said representatives from Vertex proposed installing the compressor next to a utility pole on the east side of 6800 Palm Drive due to availability of power to the compressor, ease of access for air tubes from the compressor to the lake and distance of the compressor from nearby residences.
According to the Vertex proposal, the noise level of the compressor, when installed in a Vertex “QuietAir” cabinet, “can be expected to be lower than a swimming pool pump.”
Wasserman said a similar system installed by Vertex at a pond in a neighborhood in Bradenton is “very quiet. The birds were louder than the compressor.”
Commission Chair Jim Kihm said unlike other aeration systems that create a spume of water in the middle of a lake, the Vertex system is on the bottom, reducing noise.
Commissioner Kim Rash said he spoke with several lakefront residents who previously shared concerns about the health of the lake. “Surprisingly, people seemed to be satisfied with putting the aerator in instead of dredging it out,” he said. “The ones that were most vocal seemed to be OK with it.”
Commissioner Rick Hurst asked how long it will take to see results.
Wasserman said water samples would be taken six months after the aeration is installed, this month or next, pending legal review of the contract with Vertex.
He said he is still researching marine life, such as mussels and oysters, which could consume algae to help with water quality.
“This would be the first major step to making Spring Lake a healthier lake,” Wasserman said.