Rehoboth mulls future of stormwater outfall system

Commissioners to discuss funding of further sampling
January 9, 2017

With City Hall nearly finished and an ocean outfall soon to be underway, Rehoboth Beach's next major undertaking is figuring out what direction it will take in improving the city's stormwater management system.

As part of Secretary David Small's record of decision greenlighting the ocean outfall for the Rehoboth sewer system, Delaware Department of Natural Resources and Environmental Control mandated the city submit a report on the water quality in five stormwater outfalls that empty into the ocean. The outfalls are at Grenoble Place, Maryland Avenue, Rehoboth Avenue, Laurel Street and Delaware Avenue. DNREC asked the city to explore cost-effective alternatives to improve water quality, reduce stormwater volume within the system and evaluate disposal options.

Mayor Sam Cooper said the biggest recommendation in the report submitted by engineers GHD is more information is needed before city officials can determine how to move forward. Cooper said he would like to see money put aside in the upcoming 2017-18 budget to allow GHD to conduct sampling in the water around the outfalls. The city commissioners will begin budget talks at 8:30 a.m., Thursday, Jan. 19.

GHD's report identifies enterococcus as the main bacteria tested for in the waters around Rehoboth's stormwater outfalls. Enterococcus is found in the guts of all warm-blooded animals and comes out of the body in fecal matter.

In late June, elevated levels of enterococcus bacteria led to a water advisory being issued for the area between Baltimore Avenue and Norfolk Street.
DNREC said the advisory was due to rainfall and runoff of animal droppings from birds, marine mammals or domestic pets. No human waste was detected, the department said.

The report says nationwide, stormwater runoff is the most commonly identified cause of beach closings and swimming advisories.

The report assumes high concentrations of enterococcus found in the ocean off Rehoboth are a direct result of stormwater runoff, but an exact source has not been identified.

While sampling is done twice a week during the summer, Cooper and the report said testing is not particularly detailed as to what the sources of high levels of enterococcus might be or what the effects of rainfall might be.

GHD's report identifies a number of hotspots for potential pollution including seagull feces on the Boardwalk and nearby streets, dog feces on residential properties, the Boardwalk foot showers, trash pickup locations on the streets and waterfowl feces in Silver Lake and Lake Gerar, which empty into the ocean.

However, the report says without detailed sampling, it is difficult to identify the impact of these sources.

To decrease the amount of waste getting into the stormwater system, the report recommends increased public education that takes into account Rehoboth's seasonal nature. The most basic of these methods include brochures, fact sheets, community bulletin boards and utilizing the city website.

Cooper said another easy, cost-effective waste-cutting measure is improved cleaning of the city's streets, to keep waste out of the stormwater system. Commissioner Stan Mills said the city could also do a more effective job at maintaining markers urging people to not dump waste into the storm drains.

"I believe a big part of the solution to resolve contamination of stormwater discharges will come from people and businesses not allowing contaminants to enter the stormwater drain system. Education is a key to this and can be effective and immediate while other solutions are being considered," Mills said.

The report suggests cleaning the storm drain system, to keep bacteria from growing within the pipes.

However, Cooper said this solution, while helpful, appears expensive.There are also structural alternatives mentioned in the report, such as sediment traps and sand filtration systems to remove particles from the stormwater before it reaches the ocean.

The city already has two sand filters on Wilmington Avenue that remove bacteria. To implement sand filters city-wide, the report says, would cost an estimated $736,000.

Other methods mentioned in the report include porous pavement on Rehoboth Avenue. GHD said Provincetown, Mass., a beach town similar to Rehoboth, installed porous asphalt and other drainage improvements on 103,000 square feet of road, with the project costing a total of $3.4 million. Another option for Rehoboth Avenue is permeable pavement, which the report says would come with a price tag of $2.63 million for 175,000 square feet of road.

Finally, GHD suggested extending the outfalls farther into the ocean, an option Cooper thought could be good as it would eliminate pipes on the beach as a hazard to swimmers. GHD's report estimated the cost of extending the five stormwater pipes would be $6.6 million to $22 million depending on the construction method.

Another possibility is reconfiguring the stormwater outfall system to go away from the surf zone where swimmers congregate and into a more highly diluted area. Other cities have installed new systems costing around $23 million.

Numbers like that have Cooper thinking the city needs to re-evaluate how it thinks about stormwater. Cooper says he sees stormwater as a public utility, much like water and sewer, that should be its own item in the city budget.

He said any improvements to the stormwater system have to balance water quality - which is mainly a problem in the central business areas - versus quantity, meaning areas of town that are more susceptible to flooding during large storms.

As for what's next, Mills said, "I would expect in the near future for the commissioners to discuss the report and what the next steps should be, such as, for example, to invest in additional studies including the capturing of missing data before developing additional recommendations with budget estimates."

To view the report, visit