Rehoboth testing for stormwater contaminants

After a multi-week delay caused by a root ball on Wilmington Avenue, the flushing of stormwater pipes in Rehoboth’s commercial district resumed Sept. 4.

Rehoboth Public Works Director Kevin Williams said flushing the stormwater pipe on Wilmington Avenue was expected to be done Sept. 5. Unsure how long the root ball was there, he said it was discovered when city staff began flushing the pipe a few weeks ago. The city had to wait for a contractor to run a video line to see what was causing the blockage.

There was no standing water on the streets after rain events, said Williams, because rainwater will eventually filter its way through the mess of a root ball.

The city’s streets department began flushing the stormwater pipes of Baltimore, Rehoboth and Wilmington avenues a few weeks ago as a follow-up to testing done last year, which was required as part of the permitting process for the ocean outfall project. The ocean outfall is a mile-long pipe off Deauville Beach where the city’s wastewater treatment plant sends its treated effluent. The city has been using the outfall, which cost roughly $43 million, since May 2018. Prior to that, the effluent was piped into the Lewes-Rehoboth Canal.

The results of last year’s testing, performed by city contractor GHD, showed the city’s stormwater pipes had bacteria levels considerably higher than recommended. Data showed that in the six hours immediately following six major storms, the ocean water near the city’s five stormwater outfalls averaged nearly 2,000 colony-forming units of enterococcus per 100 milliliters.

Enterococcus bacteria are found in the guts of all warm-blooded animals, and DNREC uses enterococcus levels to determine recreational swimming advisories in Delaware, with the threshold beginning at greater than 104 colony-forming units per 100 milliliters.

Williams said the goal was to clean and test the pipes while tourists were still in town and restaurants are still operating under a summer schedule. He said the delay in flushing Wilmington Avenue shouldn’t affect the results.

Williams said the majority of water flushed from the stormwater pipes is sucked up by a vacuum truck, and is not flushed into the ocean. Some does get through, he said, but ultimately almost all of that water goes to the treatment plant.

If everything goes as planned, said Williams, the city would be done cleaning the pipe Sept. 5, and GHD will be here in rain gear Sept. 6 taking samples. He said GHD has conducted tests on Rehoboth and Baltimore avenues, and he expects a package of results by mid- to late October.

Delaware Avenue stormwater pipe replacement

The testing of bacteria levels in the city’s stormwater system isn’t the only stormwater-related infrastructure project Rehoboth is working on.

During a special meeting Sept. 9, commissioners awarded a contract to replace the corrugated metal pipe that runs under the ocean block of Delaware Avenue and a section that runs under the dune, from Wilmington Avenue south to Brooklyn Avenue. Maryland-based SAK Construction was awarded the $456,000 contract.

During this year’s budgeting process, Williams described the condition of this section of pipe as dire, resulting in commissioner approval of $450,000 in the budget to fix the problem. Shortly after the budget was approved, the city put the project out to bid. During a commissioner meeting Aug. 16, Williams announced the city had received three bids for the project; two of them were right around the budgeted amount.

During the interview Sept. 5, Williams said the plan is to use the existing pipe as a form for a cured-in-place pipe. He said the new pipe has an expected life span of roughly 50 years.

“It’s a good, good product,” he said.

Editor’s note: This story first ran in the print edition Sept. 6, saying the commissioners were expected to award a contract for the Delaware Avenue project during a meeting Sept. 9. The story has been updated to reflect commissioners did vote to award the contract.