Custom-Made Device Keeps Florida Canals Clean

A modified version of the Bandalong Litter Trap collects debris from an urban drainage canal, helping to keep waterways clear in Tallahassee
Custom-Made Device Keeps Florida Canals Clean
A standard Bandalong trash containment area is 22 by 5 feet wide and needs 8 to 10 inches of water to float. The trap installed just upstream of Lake Elberta was 75 by 8 feet wide and had to function through depths of 8 feet in the 15-foot-deep canal.

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Floating debris and trash in the City of Tallahassee’s (Florida) urban stormwater conveyance system is the main maintenance challenge for the Stormwater Management Group. “There isn’t a concrete structure we could build that would capture trash from canals 20 to 40 feet wide and 15 feet deep with flows above 1,000 cfs and velocities exceeding 15 fps,” says Jodie Cahoon, P.E., stormwater management manager.

A major concern was Lake Elberta, a 20-acre regional stormwater facility downstream from Florida State University and the city’s downtown area. “I’m amazed at the number of bottles and cans that wind up in the pond, especially after football games,” says Cahoon. “These facilities are amenities, and large amounts of trash bobbing in them is unsightly.” The lake had a trash-capture device, but it was ineffective.

Then Cahoon met Jason Davis, product manager for Storm Water Systems (SSS), at the Florida Stormwater Association annual conference. Davis accessed conditions at the lake and recommended a modified version of the company’s Bandalong Litter Trap.

“His engineers were unaccustomed to dealing with flows, velocities, rainfall amounts, and water levels as high as ours,” says Cahoon. “They worked with our engineers and accomplished something SSS has never done before.”

A standard Bandalong trash containment area is 22 by 5 feet wide and needs 8 to 10 inches of water to float. The trap installed just upstream of Lake Elberta was 75 by 8 feet wide and had to function through depths of 8 feet in the 15-foot-deep canal. Its installation was a joint venture.

“Our crews used boats or waded in chest-deep water to install components as they were lowered by city cranes with long booms that reached out over the canal,” says Cahoon. “ Jason’s crew installed shore elements and used their technical expertise to fine-tune the trap.” The boom rides on metal columns with rollers, enabling it to rise and fall with the water level. A curtain on the boom hangs 2 feet below the surface to snare submerged trash.

How frequently city crews clean the trap depends on rainfall, but it’s usually eight to 10 times a year. They check the trash volume monthly and after significant rainfalls. “The best way to remove 10 to 15 cubic yards of material from the trap is with a clamshell bucket and garbage truck,” says Cahoon. “The operator grabs material with the bucket, lifts and dewaters it, then deposits the load in the truck.” Dewatering continues on the ride to the disposal facility.

Tallahassee has earned high honors for its innovative and comprehensive stormwater management program, read more about the Stormwater Management Group in the February 2016 issue of MSW.



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