Daly City completes repairs to underwater outfall pipe 

Divers recently completed crucial repairs to Daly City’s submarine outfall, a complex pipe mechanism that extends a half-mile into the Pacific Ocean at Fort Funston and discharges clean, nonpotable water from the city’s sanitary sewer system.

Tom Piccolotti, the collection and distribution systems manager for the city’s Department of Water and Wastewater Resources, said the project’s successful completion is the culmination of a repair process that began 18 months ago. The work was initiated after divers discovered that vital parts of the pipe system had come off or had been destroyed, and determined during another dive in July that additional parts needed to be replaced, he said.

Piccolotti said the contractors performing the inspections and repairs faced danger and logistical challenges with every dive because the outfall device is under 50 feet of water.

“It’s one thing to be in the Bay doing that kind of work,” Piccolotti said. “It’s another to be in the Pacific Ocean with its swells and strong, shifting currents.”

Elaborating on the technical details of the project, Piccolotti explained that on the last 200 feet of the 33-inch-diameter outfall pipe, there are 13 diffusers containing one-way valves that release treated wastewater but keep sand out. He said the end of the pipe is partially closed by a smile plate, which is a cap designed to let some water out, while at the same time maintaining enough backpressure so the diffuser valves can function properly.

The inspection performed 18 months ago revealed that most of the diffusers had some parts that were beyond repair, Piccolotti said. The pipe rehabilitation included replacing missing nuts from four of the six bolts that hold the smile plate in place and replacing missing straps that hold other pieces in place. Now that the work is done, Department of Water and Wastewater Resources Director Patrick Sweetland said, the system “has had its as-built condition re-established.”

In other words, the outfall is as good as new, he said, but the city will have to keep a close eye on the condition of the equipment to ensure no future problems arise. He said while the city’s practice has been to inspect the underwater system every five years, internal discussions are taking place to determine whether to shorten the interval between inspections.

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