UPDATE 'No swimming' advisory lifted in Rehoboth Beach
UPDATED JUNE 24: A swimming advisory for Rehoboth Beach has been lifted after bacteria levels decreased below the state and federal standard for concern.
Bacteria levels dropped to 10 colonies per 100 milliliters of water in the latest sample of water collected off the ocean in Rehoboth Beach Thursday.
The findings prompted state environmental officials to lift a swimming advisory for the ocean from Rehoboth Avenue south to Norfolk Street.
The state's benchmark for issuing an advisory in ocean waters from a single test if 104 colonies per 100 milliliters of enteroccocus bacteria. The single sample from Rehoboth Beach collected on Wednesday was 135 colonies per 100 milliliters.
Debbie Rouse, the state shellfish and recreational waters program manager said it is likely that heavy rain, more than an inch fell in the area on Tuesday, caused the increase in bacteria levels when the single sample was collected Wednesday morning.
Stormwater in Rehoboth is discharged into Lewes & Rehoboth Canal, the lakes in the city or through networks of pipes that flow into the ocean.
That stormwater from streets, rooftops, parking lots, sidewalks and residential lawns can contain everything from bird and other animal waste to food and petroleum resident. Previous tests done by the city showed there were no sources of human contamination.
While the city is proposing a new ocean outfall to dispose of treated sewage waste, the ocean is not yet the discharge point. Treated wastewater goes into Lewes & Rehoboth Canal near the entrance to Rehoboth Bay.
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State environmental officials have issued a water quality advisory for Rehoboth Beach in the near shore ocean from Rehoboth Avenue to Norfolk Street because of elevated bacteria levels.
City officials posted advisory signs on the back of lifeguard stands Thursday but the beach and ocean are still open, said Rehoboth Beach City Manager Sharon Lynn.
"We don't ban people from swimming," she said.
The Rehoboth area got 1.02 inches of rain on Tuesday, the day before state officials took one sample from the ocean just off the beach.
Heavy downpours are often associated with higher bacteria levels, especially in urban resorts like Rehoboth Beach. Runoff from the streets can cause elevated bacteria levels. Over one hour on Tuesday .72 of an inch fell at nearby Lewes, according to data on the University of Delaware Environmental Observing System. No data was available for the station on the Rehoboth boardwalk.
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Debbie Rouse, the state manager of Shellfish Safety and Recreational Water Monitoring, said that the heavy rain was the likely cause of the elevated bacteria reading.
An advisory is issued when bacteria levels in ocean water exceeds 104 colonies per 100 milliliters of water. The sampling tests for enterococcus bacteria. High levels of enterococci can come from bird and other animal waste. The Rehoboth sample measured 135 colonies per 100 milliliters.
Rouse said that a resample was taken Thursday and results will be available on Friday. It is likely, she said, that the advisory will be lifted.
Rehoboth was the only sampling location between Slaughter Beach and Fenwick Island that had elevated bacteria, she said.
"It's the rain," she said. "It definitely was the rain."
The city is studying ways to reduce runoff pollution as part of an agreement with state environmental officials that was linked to a proposed ocean outfall, which would dispose of treated sewer waste about a mile off the shore. Several city streets drain into the ocean through pipes that are connected to jetties and extend out into the ocean just beyond the beach.
Rehoboth rarely exceeds the state swimming water standards and in recent years has been recognized with a Blue Water award because of high swimming water quality.
Rouse said a healthy swimming won't likely be at increased risk but children, the elderly and people with compromised immune systems should avoid swimming until the bacteria numbers fall within the safe limit.
The most common ailments are gastrointestinal disorders and ear and nose infections, Rouse said.
Reach Molly Murray at (302) 463-3334 or mmurray@delawareonline.com. Follow her on Twitter @MollyMurraytnj.