Freshly pumped sand appears dark when first spread on the original beach,
but is expected to lighten over time.
Jerry Lower/The Coastal Star
By Cheryl Blackerby
Florida Department of Environmental Protection scientists took water samples at the Ocean Ridge dredging site Jan. 28 to monitor levels of turbidity, the cloudiness of water caused by suspended solids such as silt.
The testing was in response to Reef Rescue’s recent samples that showed high turbidity levels.
“We’ve been monitoring the project, and we found turbidity levels in excess of the permit standard of 29 NTU (nephelometric turbidity units),” said Ed Tichenor, director of Palm Beach County Reef Rescue. “We’ve gotten levels as high as 248 NTUs. When we get these high readings and the dredge company is getting readings in compliance, then DEP tries to determine the reason for the discrepancy.”
DEP reports were not finalized Jan. 28, but a scientist with the Palm Beach County Environmental Resources Management, who went along on the boat with DEP, found the samples were in compliance, said Tracy Logue, coastal geologist for the county’s environmental department.
“The monitoring methods and the test results were in accordance with permits and the results were acceptable,” said Logue.
The DEP testing may indicate the water is clear, but Tichenor said those tests may be the result of the dredge not working for several days. Reef Rescue is monitoring the silt plume caused by the dredge with aerial photography. So far, he said, silt has not settled on the coral.
Silt can be a problem both for the beach and the coral reef, he said. “If the project generates too much silt it smothers the coral. Silt washes off the beach and ends up on the coral. It has very light traction, and the more silt there is on the beach, the more unstable the beach is.”
County inspections have shown the beach sand to be satisfactory, said Logue.
“I’ve been looking at the sand every day and it looks acceptable to me,” she said.
Dredging for the Ocean Ridge beach renourishment project started Jan. 12 after several weather delays and holidays.
Work was forced to stop yet again Jan. 21 because of high winds and rough seas. The dredge moved back to Ocean Ridge Jan. 25, but spent several days moving submerged pipe to a new borrow area. Work resumed after DEP testing Jan. 25, said Logue.
The Ocean Ridge project should be completed by Feb. 10 barring bad weather, she said. Sand is being pumped onto the beach starting at the Ocean Club and ending at Edith Street.
The beach will be about 300 feet wider than it was pre-dredging, she said. The new sand is darker in color than the original sand, but has already lightened on the 1.1-mile beach project. The sand is being dredged from borrow areas about 1,800 feet offshore.
After the Ocean Ridge project is finished, the dredge immediately will move to Delray Beach, she said. The dredge then will go to the north Boca Raton beach. There are no completion dates set for the Delray Beach and north Boca Raton beach renourishment projects.
The dredge originally started work in Ocean Ridge Dec. 19 after completing a beach project in south Boca Raton.
The renourishment projects in Ocean Ridge, Delray Beach and north Boca Raton are U.S. Army Corps of Engineers beach projects. The Army Corps deadline for those projects is April 30 and the work is expected to be finished well before the deadline if seas remain calm.
The south Boca Raton beach renourishment is not an Army Corps project, but the city used the same contractor to save money.
After delays from bad weather including high winds during most of November, the beach project in south Boca Raton finally started the day before Thanksgiving and finished pumping sand on .9 miles of beach Dec. 9.
“The dry beach was widened 60 feet on average the entire length,” said Jennifer Bistyga, engineer with the city of Boca Raton.
Meanwhile, excavation of the Boynton Beach Inlet sand trap is expected to continue until June, said Logue.
The non-beach-compatible sand is being transported to the Grassy Flats Lake Worth Lagoon Restoration Project, which includes the building of two mangrove islands 4 miles north of the inlet on the east side of the lagoon near the Palm Beach Par 3 Golf Course.
The project, which will create 10.5 acres of seagrass habitat and 1.1 acres of salt marsh, will increase the food and nursery habitat for fish, manatees and wading birds while improving water quality.
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