Photos by Reef Rescue (top) and Chase Bilbery
By Cheryl Blackerby
The dredge is gone. It left Delray Beach on April 15 for New York.
Offshore sand has been pumped onto 1.9 miles of shoreline. The job is done for, theoretically, another decade or so, barring hurricanes.
Residents who had looked at narrowed beaches and escarpments carved out by Hurricane Sandy in late October can rest easy. The shoreline is now reinforced with more than 1.6 million tons (1.2 million cubic yards) of sand.
The $9.2 million project, part of a 10-year renourishment plan that happened to coincide with damage from Sandy, is completed.
There were bumps along the way — tugboat lines dropped and dragged across Flower Garden Reef when the barge moved from the Port of Palm Beach to Delray Beach, work stoppages due to rough seas and mechanical problems, and a silt plume running several miles along the coast.
It’s the silt that has Ed Tichenor worried.
Tichenor is director of Reef Rescue, a nonprofit group of divers that monitors Palm Beach County’s reefs. He owned an environmental testing laboratory in New Jersey and he has put his knowledge to work in Florida.
During the dredging, Tichenor monitored the turbidity — silt and other suspended matter in the water. The dredge’s permit required the turbidity to stay below a certain level outside the dredge’s “mixing zone,” where the sand is pumped from holes in the ocean floor.
“I began to see turbidity levels that were quite high,” he said. Tichenor’s numbers contradicted the samples taken by the dredge contractor, which were low.
He contacted the Florida Department of Environmental Protection, and soon after a FDEP representative and Tichenor together took samples, which again were high. “We watched a contractor take a sample and it failed. The next day, the DEP and I took another sample and it failed again,” he said.
When the level exceeds permit requirements, the dredge must shut down, said Tichenor, adding that the dredge had to shut down for several hours on four days because of high turbidity.
An FDEP spokesperson confirmed that silt levels were high.
“There were five instances where the subcontractor, CZR (the turbidity monitoring subcontractor for the Delray project), reported turbidity excedances and construction activities were discontinued until the turbidity returned to acceptable levels, as required by the permit. No warnings or citations were issued and the project is complete,” said Mara Burger, spokesperson for the FDEP.
And she had an explanation for the conflicting turbidity readings. “The differences were that while all samples were being taken from the densest portion of the plume, the samples were taken in different locations, which resulted in different readings by the various parties,” she said.
And the silt plume left behind? “Sometimes, as a result of new beach material a small residual plume can occur,” she said.
In the two weeks after the dredge left, the plume dispersed, said Tichenor, and settled on the coral reefs, which is what worries him.
“There’s no longer a visible plume, and now the silt has dispersed in the system and may persist for years, slowly degrading the reef,” he said. “There is no requirement to make that connection between dredging and later damage to the reef.”
Silt, a sediment with a consistency between fine sand and clay, has settled on parts of the reef system from Delray Ledge at the north end of the project to Seagate Reef on the south end, a little less than a mile, he said, adding that the entire reef hasn’t been inspected yet by Reef Rescue divers.
The silt is causing stress to already-stressed coral and can ultimately kill corals, he said. The silt can harm corals in several ways, all of which are deadly to a reef system.
“The coral generates mucus and expends a lot of energy trying to get the silt off. The silt lowers the light level and corals depend on sunlight to live. And the silt can smother the coral to the point that it may die,” he said.
Silt also affects spawning, which occurs in August and September. The larvae usually settle on hard rock and starts another colony, but if silt is on the rock the larvae can’t attach, he said.
One of Reef Rescue’s network of divers, Chase Bilbrey, took photos of the reef a week after the dredge left, and showed them to Tichenor.
“The ‘before dredging’ and ‘after dredging’ photos are shocking,” said Tichenor. “A lot of silt is in the water and turned everything blue and you can’t see the bright colors of the coral. They aren’t getting enough light and they have a coating of silt.”
Delray Beach’s reefs are in trouble, and area residents should be concerned, he said. “The corals have diseases, they’re impacted by anchoring, climate change — it’s death by a thousand cuts.”
A big problem, he says, is lack of regulatory oversight in this area and the need for monitoring.
“Once an incident is reported by local volunteers, then DEP will do a survey and take enforcement action,” he said.
It was a dive boat captain, he said, that brought the damage to Flower Garden Reef to the FDEP’s attention.