The Coastal Star

Ocean Ridge: System to capture runoff is among ideas to control Inlet Cay flooding

By Dan Moffett

The much anticipated engineering report on Ocean Ridge’s Inlet Cay neighborhood is giving residents a clearer picture about why their streets routinely flood after heavy rainfalls.

Consultant Robert Higgins told town commissioners on Aug. 6 that the 60-year-old, 16-acre manmade island has more than its share of drainage issues to resolve.

Higgins said that the drainpipes are too small to meet modern standards and some of them need repairs.

In addition, a layer of peat and muck covers nearly all the island and over time it has compacted to the point where water cannot penetrate it. The houses are not settling because they’re built on pilings, he said.

“But everything else is settling,” he said.

“The layer of muck is compressing and that’s why you see some of the driveways are dropping,” Higgins said.

The water has nowhere to go during a heavy rainfall, because of the dense layer of muck. He said rainfall is solely responsible for the street flooding, refuting theories by some residents that an artesian spring contributed to the problems.

“Water cannot move downward, therefore water moves laterally into the streets,” Higgins said, “primarily from east to west on Spanish River Drive.”

Higgins, the eponymous president of his West Palm Beach engineering firm, offered several recommendations for limiting the flooding. First, he told commissioners to continue their aggressive maintenance and repair program of the town’s stormwater pipes, using closed-circuit television cameras to find breaks and blockages.

He suggested using a Stormceptor filter in the Inlet Cay neighborhood. The device costs about $18,000 installed and removes sediments, oils and pollutants from discharges.

Higgins also suggested adding exfiltration trenches along the roadsides. These are 12-inch perforated pipes that capture excess runoff and provide extra flood storage. He estimated the cost of a trench system at about $40,000.

Several other options come with significantly bigger price tags. Replacing paved street surfaces with permeable pavers costs about 10 times more than asphalt, Higgins said. Adding a pump station is impractical because the town would have to buy property to put it on. Continuing to raise the street levels isn’t cheap either.

Mayor James Bonfiglio said the commission would discuss Higgins’ report during the current budget deliberations, with an eye on making improvements over the next few years.

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