Posted August 13, 2019
SOUTH PATRICK SHORES — Workers cleared a tight space this week just south of Pineda Causeway to forge a temporary storage area for enough soon-to-be-dredged organic muck from the bottom of Grand Canal and surrounding canals to fill 26,611 dump trucks.
The $26.4 million project will deliver deeper, cleaner canals by November 2022, and a replanted and completed muck management area by February 2023.
But first, it'll bring lots of heavy diesel equipment, trucks and a dredge. Brevard County officials assure residents that workers will keep noise, odor and traffic disruptions to a minimum, to the extent possible.
The project removes thousands of pounds of nitrogen and phosphorus that fuel toxic algae blooms in the Banana River Lagoon. It is the most complicated local dredging project to date in the county's $486 million Indian River Lagoon cleanup plan, officials say. The dredge must work among densely populated residential canals, frequented by government-protected manatees, and haulers must carefully load muck and exit along a heavily trafficked causeway.
"It is very complex," said Walker Dawson, and engineer with Brevard County and the project manager on the dredging. "There are so many nuances and challenges"
Gator Dredging of Clearwater is expected to begin Oct. 1 removing 479,000 cubic yards of muck from Grand Canal, three entrance canals and 16 residential finger canals south of Pineda Causeway. Muck is formed from rotted algae, grass clippings, and stormwater runoff containing silt and clays.
"We're not disturbing the muck and releasing big plumes of the nitrogen and phosphorus into the water column. It's like a glorified vacuum cleaner," Dawson explained of why the county often opts for a hydraulic dredge, instead of mechanical excavation dredging.
Under state and federal permitting rules, the dredge will have to shut down periodically to accommodate manatees, when one is seen near the dredge and during winter months when seacows congregate in canals to keep warm, from Nov. 1 to May 31.
They also won't dredge on weekends, to avoid disrupting boating.
"We want people to pay attention to what's going on out there, Dawson added. "The pipeline will be submerged ... We do wan't people to steer clear of the dredge itself."
Workers will use 12 sets of "geotubes" that will be lined up, and will sequence the filling of those tubes with the dredged-up muck to remove the water. There will be a swale along the perimeter to decant the water to a cell where the tube sits. The water will then go into a water-treatment system that will remove nitrogen and phosphorus.
Similar treatment systems have been used in Lake Apopka.
The reinstatement process will prevent 72,660 pounds from being returned back to the lagoon, Dawson said.
After most of the water flows out of the muck, trucks will haul it to Platt Ranch, at the south side of U.S. 192, west of Interstate 95, where the muck will be tilled into the ground to fertilize pastures.
Permit requirements dictate that the muck test within state and federal guidelines for metals, PCBs, pesticides and other contaminants. But separate from permit requirements, the county tested the area for per- and poly fluorinated alkyl substances (PFAS), which have been found in wells countywide and in the Indian River Lagoon.
Residents have been raising concerns that those compounds may be contributing to cancers and other illnesses near Patrick Air Force Base, which used firefighting foams that contained the chemicals. The chemicals also appear in common commercial products, especially flame-resistant materials. State health officials earlier this year concluded there was no "cancer cluster" in Brevard linked with the chemicals, but some concerned residents have criticized the state's investigation as insufficient.
The Grand Canal dredging project is funded by $18.2 million from the county's special lagoon sales tax, with the rest coming from a state grant. County officials last year predicted the lagoon sales tax that Brevard County voters approved in 2016 will raise $486 million over a 10-year period.
County officials are urging residents along canals to take steps to reduce fertilizer runoff and other backyard activities that promote muck buildup, especially from grass clippings.
"The intent is to keep all the grass clippings in the yard," Dawson said.
Jim Waymer is environment reporter at FLORIDA TODAY.
Contact Waymer at 321-242-3663
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