When high levels of enterococci were recorded at Lewes Beach June 5, a cavalcade of theories as to the source of the problem flooded social media.
Many pointed to the ocean outfall that recently had days earlier gone online off the coast of Rehoboth Beach, while others circulated a rumor that the Lewes Board of Public Works had allowed untreated waste to be dumped into the Lewes-Rehoboth Canal.
Michael Bott, environmental scientist with DNREC’s Shellfish and Recreational Water Program, said the most likely culprit is wildlife, particularly horseshoe crabs and birds migrating along the Delaware Bay.
“The more natural a habitat, the more bacteria in the water,” he said. “If you have a healthy wildlife population, they all poop. That poop gets washed into the bay water, particularly after storms.”
The days and weeks leading up to the June 5 advisory were rain-soaked, with higher-than-normal precipitation, weather records show.
Bott said DNREC issues advisories, and it is up to each municipality to make a decision on swimming restrictions. He said despite the advisory, the risk to humans is very low.
“The greatest at-risk populations are people who have compromised immune systems and also the elderly and very young,” he said. “If you’re concerned, don’t immerse your head. The risk is greatest when you’re ingesting the water.”
The water is tested weekly for Enterococci at 24 locations along the ocean and bay beaches. Testing occurs twice a week at Cape Henlopen State Park, Rehoboth Beach, Dewey Beach, Bethany Beach and Fenwick Island, Bott said.
Water testing is required by the Environmental Protection Agency, established in 2000 by the Beaches Environmental Assessment and Coastal Health Act. enterococci is an indicator organism that helps identify where fecal contamination has occurred and where disease-causing microbes may be present. The EPA found, through public health studies, that enterococci is a very good predictor of illness in all waters. But because Enterococci is present does not mean swimmers will get sick, as indicator organism do not generally cause illness, the EPA says.
Elevated levels are sporadic, but not uncommon, Bott said. At Slaughter Beach, in particular, five advisories have been issued since July 2017, including four since May 24. Bott said that’s likely because of the high concentration of horseshoe crabs this time of year. The crabs also attract a higher number of shorebirds to the area.
Advisories, he said, are mostly unavoidable. The only human-related variable is pet waste, he said. If people do not clean up after their pets, the waste could be added to the stormwater system.
“All stormwater goes somewhere,” he said. “Cleaning up pet waste can reduce levels.”
So what are the chances elevated levels of enterococci are caused by human waste discharged through an outfall?
“With dilution offshore, the risk is very low,” he said. “It’s much more likely related to wildlife or domestic pet sources. On the Delaware Bay, it’s much more common this time of year.”
As for that rumor about the Lewes BPW dumping untreated waste into the canal, General Manager Darrin Gordon says it’s not totally unfounded, but it definitely could not have contributed to the June 5 advisory.
“We found back in 2016 that two of our wastewater connections on Savannah Road were still tied into a storm drain,” he said. “We fixed it immediately.”
He said before the fix, an unknown amount of wastewater did discharge into the canal, and he does not know how long it had occurred before it was fixed.
All of the city’s wastewater now goes directly to the wastewater treatment plant on American Legion Road, where it is treated and discharged into the canal.
“We have a National Pollutant Discharge Elimination System permit, and we are way below all of our water quality requirements,” he said. “We have some of the best quality water going into the environment than any other wastewater treatment plants in Delaware and possibly the East Coast.”
For anyone curious about how it works, he said, he is more than willing to give a tour.