SULLIVAN’S ISLAND — Recent heavy rains that doubled the flow into the wastewater treatment plant Wednesday caused a spill of 101,000 gallons of treated “suspended solids” that has temporarily closed shellfish harvesting from Ben Sawyer Bridge northeast to Conch Creek, officials said.
The area affected by the wastewater effluent overflow is about a mile long.
“Nothing has spilled out onto the ground. We exceeded our effluent level for suspended solids,” said Greg Gress, general manager of the Water and Sewer Department.
The town is permitted to discharge up to 570,000 gallons of treated wastewater per day into Cove Creek, which drains into the Atlantic Intracoastal Waterway. The temporary shellfish bed closure happened because of elevated bacteria levels associated with the spill, according to the state Department of Health and Environmental Control.
“The affected areas will reopen once water quality data indicate the bacteria levels are acceptable for shellfish harvesting,” said Mike Pearson, DHEC shellfish sanitation section manager.
The spill happened from 5 a.m. to 7:30 a.m., according to the Water and Sewer Department. “During this short time period high bacterial levels may have been discharged as well,” the department said.
The event was the second one of its kind in recent months.
On Aug. 31, about 470,000 gallons of treated wastewater overflowed at the plant when torrential rains overwhelmed the system, which is designed for brief peak flows of 2.5 times its permitted capacity.
On Aug. 28, Mount Pleasant Waterworks leaked an estimated 500,000 gallons of sewage that drained into ponds at the Seaside Farms subdivision on Rifle Range Road. The spill happened because of corroded pipe and increased pumping pressure due to heavy rains.
Afterward, clam harvesting was temporarily shut down behind Isle of Palms.
Too much stormwater seeping into old, cracked pipes can create too much of a burden on a treatment system, Gress said.
“We have the problem, but so does everybody else in the nation. It’s a big issue. It’s not a cheap fix,” he said.
Gress said the town is looking at the possibility of using a technology called “chemical grouting” to fix old pipes.
The wastewater plant serves about 2,000 island residents.