Why you should avoid the ocean after it rains
A day after a heavy rain hit Rehoboth Beach earlier this summer, Michael Bott grabbed a sample from waist-deep water off Rehoboth Avenue, packed it in ice and took it back to the lab for testing. It was a routine test, one like dozens of others that he gathers from May through September along the coast.
But this time, there was a difference. Bacteria levels, normally low along this part of the coast, measured at 135 colonies per 100 milliliters of water, triggering state officials to issue a swimming advisory. Any reading over 100 activates an advisory in ocean water.
It confirmed what many already know both in Delaware and other coastal states. When it rains, the runoff that is collected in a network of pipes ultimately ends up in the ocean where people swim.
In Rehoboth Beach, there are five pipelines that drain the city's stormwater into the ocean just off the beach. No one is sure what's in the runoff because it's never been tested here along the Delaware coast. What they do know is there does seem to be a correlation between heavy rain and elevated bacteria in the water.
Bott spends a lot of time in the water collecting the samples that are tested to make sure Delaware beach-goers know that the water off Delaware's coast is safe for swimming – at least when it comes to a bacterial indicator.
Rehoboth doesn't, as of yet, discharge treated wastewater into the ocean and there are no interconnections between storm and wastewater collection systems. He takes reassurance from that. When bacteria levels do rise, it's likely from pet and wildlife waste, he said.
But as state officials have assessed Rehoboth's request to begin discharging treated wastewater a mile off the coast into the ocean, state environmental officials started to also think about the city's stormwater outfall network.
"We're talking about ocean water quality," and Rehoboth's "five-star status" as a high-quality recreational swimming beach, said state environmental secretary David Small.
STORY: Tropical Storm Hermine lumbering toward Delaware
STORY: Even cops surprised by Delaware beach traffic stunts
Small said that as his staff discussed the city's request for an ocean outfall for treated sewage waste, the stormwater issue came up as "an equally important issue."
Two years ago, as Small was signing off on initial paperwork for the ocean sewage pipeline, he required the city to undertake a preliminary review of the stormwater system.
The findings, completed by a consulting engineer late last year, are inconclusive on what the best possible solution is. As it turns out, computer modeling indicated that extending the pipelines out beyond where people swim may not make much difference in heavy rain. In the 24 hours after a heavy rain, the models suggest that the stormwater plume sloshes back and forth with the rise and fall of the tide and lingers near the shoreline, said Jeff Sturdevant, the GHD consultant who worked on the study.
Rehoboth already uses sand filters in some of its stormwater collection systems and those could help improve water quality, he said. And the city has an aggressive street sweeping program to reduce the impact of rubbish on stormwater.
But in the end, a dirty diaper dumped in the street might be enough to cause bacteria levels to rise in the ocean during a heavy rain, he said.
State tourism officials estimated earlier this year that eight million people visited Delaware in 2014 and they stayed an average of 2½ days. Tourism contributed $3 billion to the state's gross domestic product and the industry generated $470 million in taxes and fees for state and local government. Much of that traffic comes to the state's beaches.
A University of Delaware Center for Marine Policy Study found that a strong coastal tourism economy doesn't happen by chance and includes local efforts to makes sure beaches are wide, fisheries are sustainable and waters are clean.
In July 1988, for instance, medical waste started washing up on beaches in New York and New Jersey. Beach closings that summer cost the two states an estimated $1.5 billion.
Raising awareness
More than a decade ago, Stan Mills got interested in what was going into Rehoboth's storm drains. He worked with city officials to get a grant and marked all 622 storm drains with circular medallions that let people know the drains flow to the ocean.
"Every storm drain terminates in one of our water bodies," he said. And ultimately, it all ends up in the ocean.
Even with the signs, Mills said he still sees people rinsing paint cans into the storm drains or kicking dog waste into them. Some restaurants rinse kitchen floors and the wash water goes to the storm drain, he said. People throw grass clippings in them, too, he said.
"It's not widespread," he said. "But it only takes a few."
STORY: Shucks! Don't pitch those oyster shells
STORY: Business community eyes Coastal Zone Act change
Mills, who now serves on the city commission, said he is reading through the draft stormwater report to see what other steps the city can take to improve water quality.
He and Small are not alone in their concerns.
"Are we going to be reactive on this or are we going to be proactive," asked John Doerfler, chair of the Surfrider Foundation, Delaware Chapter. "Most people have no idea" that the accumulated debris on streets, sidewalks and rooftops washes clean during heavy rains and ends up in the ocean. "It's untreated waste."
And when there are elevated bacteria levels, "it's those mysterious birds" that are blamed, he said.
Most surfers know to stay out of the ocean after a heavy rain, he said.
For several years rainfall was a trigger that was used in Rehoboth Beach for swimming advisories.
In 1990, city officials hired Vincent Olivieri, an epidemiologist at Johns Hopkins in Baltimore, to look at stormwater impacts in the city. At the time, state health officials were looking at a rainfall standard that would trigger beach swimming advisories. Rehoboth's rainfall triggers were steep because of the city's stormwater outfall system and city officials wanted to prove the system wasn't impacted by human sources of waste.
The study found no sources of human waste and state officials ultimately relaxed the rainfall trigger to 3 inches of rain within a 24-hour period as the benchmark to recommend a swimming advisory. Rainfall like that is rare in Rehoboth Beach. This summer, the heaviest rain in 24 hours was 2.14 inches on July 20. The June 22 high bacteria readings came after a 1.04-inch rain on June 21.
Some suggest the impact of rain is worse when it has been dry for weeks at a time. Others say that water monitoring programs will only capture elevated bacteria if the water is sampled after a rain.
The state Department of Natural Resources and Environmental Control, which oversees recreational swimming water testing, follows protocols put in place by the federal Environmental Protection Agency. The five most popular ocean beaches are tested twice a week on Mondays and Wednesdays, Bott said.
Quick remedy may be needed
Except for that one high reading in June, Rehoboth's bacteria counts have been well below the trigger for an advisory. Dewey Beach and Bethany Beach each had one bacteria advisory this summer, too.
One problem in Rehoboth Beach is that along the Boardwalk, there is little green space and lots of impervious surfaces. The city's infrastructure was built out decades ago, long before people thought about the environmental impact of stormwater runoff. Small said the city is too small to fall under federal EPA guidelines for stormwater management.
But in other states, where clean beaches and pristine oceans are also huge economic and tourism drivers, local officials are quickly ramping up steps to reduce pollution to the ocean when it rains.
In Dare County, North Carolina, a multi-year study has been underway to sample the stormwater going into the ocean in Kill Devil Hills and Nags Head. Ultimately, the findings will be part of a master plan for better stormwater management.
In Massachusetts, state officials have developed a green infrastructure plan to help coastal communities design grassy buffer strips, plant rain gardens and take other steps to reduce the impact of stormwater on the shoreline.
In both North Myrtle Beach and Myrtle Beach, South Carolina, city officials are spending millions of dollars to combine stormwater pipes. The two resort cities are much larger than Rehoboth Beach and are required to meet federal EPA guidelines for stormwater management.
STORY: YUCK! Rehoboth cited for sewer discharge
STORY: Caribbean blue waters elude Delaware beaches
In North Myrtle Beach, city officials spent about $9.5 million to combine five outfall pipes and divert stormwater into one large one that will discharge stormwater about 1,000 to 2,000 feet beyond the beach. In Myrtle Beach, city officials are spending $10.4 million on a similar project.
The idea is to reduce the potential of bacteria pollution in swimming areas.
With the old stormwater pipe system, the pipes were underwater at high tide and exposed at low tide, said Kevin Blayton, the director of public works for North Myrtle Beach.
Blayton said the new, single pipe will discharge stormwater in 25 to 30 feet of water where there is less potential impact on swimmers,
Besides the central discharge pipeline, the city has also installed upstream devices to remove debris and grease and pre-filter the stormwater.
Even though Delaware's beach communities don't reach thresholds for stormwater management mandates, on a busy summer weekend, ocean coast population can swell to well over 100,000 people, complete with urban-style traffic jams, parking woes and blanket to blanket crowds.
Small said the draft report is the first step in better understanding Rehoboth's stormwater issues.
"It really did a pretty good job," he said. But "a lot of additional data would be needed" to determine what happens next.
Reach Molly Murray at (302) 463-3334 or mmurray@delawareonline.com. Follow her on Twitter @MollyMurraytnj.
Highlights of the Draft Stormwater Report
Rehoboth has five ocean outfalls for stormwater: Grenoble Place; Maryland Avenue; Rehoboth Avenue; Delaware Avenue and Laurel Street. In addition, Silver Lake ultimately drains to the ocean. That pipeline is managed by the state.
The report assumes that high bacteria levels in the ocean are the direct result of stormwater runoff but the source has not been identified
Bacteria is everywhere. A study done in Monmouth County New Jersey found baseline bacteria levels in commercial areas as high as 8,500 colonies per 100 milliliters and as high as 6,500 in residential areas.,
There are some potential hotspot triggers: waterfowl at Silver Lake and Lake Gerar, which are waterfowl sanctuaries; gulls at the Boardwalk and nearby side streets where food is sold; dog waste throughout the city; foot washes along the Boardwalk and trash pickup areas where trash residue leaks and accumulates.
Public education may be an important tool in reducing bacteria impacts.
Extending discharge pipes may not be effective. Models found that the stormwater plume lingers with the rise and fall of the tide for 24 hours after a rain.
Recent peak bacteria counts and associated rainfall
June 22, 2016 – 135 colonies per 100 milliliters of water at Rehoboth Avenue – followed 1.04 inches of rain
June 3, 2013 – 703 colonies per 100 milliliters of water at Rehoboth Avenue and 183 colonies per 100 milliliters at Virginia Avenue – followed 2.12 inches of rain
August 8, 2012 – 199 colonies per 100 milliliters of water at Rehoboth Avenue – followed 1.1 inches of rain.
What you can do
- Pick up after pets
- Don't dump anything in storm drains
- Don't feed the gulls
- Dispose of trash properly
- Using a foot wash in Rehoboth? Use it only to rinse sand off the feet.