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Underwater cutter: A weed management alternative

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TVA River Neighbors
august 2006

 

Underwater cutter: A weed management alternative

The early growth and expansion of Eurasian watermilfoil in Guntersville Reservoir this spring presented a challenge for North Marshall Utilities (NMU), which supplies water to approximately 3,900 customers near Grant, Alabama.

image of cutterEurasian watermilfoil is an invasive plant introduced to North America in the 1940s, probably by aquarium owners. It can form thick underwater stands of stems and vast mats of vegetation on the water’s surface. These mats can clog propellers, bother swimmers, restrict boating and fishing access, and affect the ecology of a water body by crowding out important native aquatic plants.

Milfoil mats also can clog water intake pipes. In NMU’s case, a buildup of plant fragments on an intake screen in the Honeycomb Creek embayment reduced the volume of raw water for processing by approximately 25 percent.

Danny Bates, manager of NMU, contacted TVA in early May for assistance in addressing the problem. In response, TVA loaned NMU an underwater weed cutter on a short-term basis to remove milfoil growing in the vicinity of the intake.

The cutter, manufactured by the Hockney Company, was purchased in partnership with the Tennessee Wildlife Resources Agency for use in demonstrations. It is a self-propelled pontoon boat with a 10-foot sickle bar that is capable of cutting plants to a depth of five feet below the surface.

NMU cut approximately two acres of milfoil from the vicinity of the intake, which allowed self-cleaning of the intake screen by backwashing.

“Removal of the milfoil from around the intake allowed us to resume normal operations at our plant,” said Bates. “We appreciate the loan of the cutter and TVA’s assistance in helping us to solve the problem and meet the water demands of our customers.”

Small mechanical weed cutters offer advantages in selected areas. They can work in shallow waters not accessible to large mechanical harvesters, they provide an alternative to herbicide control, and they tend to be more affordable than some other control methods.

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