Petersburg is going through the same problem that Wrangell confronted last September: Its sewage outfall line is broken.
Petersburg officials discovered that the diffuser section at the end of the outfall pipe, which disperses treated effluent from the wastewater treatment plant into Frederick Sound, had become detached from the line.
The outfall pipe extends about 800 feet offshore, reaching a depth of 60 feet, to disburse the sewage into the larger waterbody with strong currents.
It’s not known when the line was damaged.
“At some point in the past 35 years, something caused the roughly 16,000-pound line to move and the joint to fail,” Justin Haley, Petersburg’s wastewater operations supervisor, said last week. “A ship’s anchor catching and dragging the line is the most plausible explanation.”
That’s what happened last September, when a boat pulled up its anchor and hooked and damaged Wrangell’s deep-outfall pipe between City Park and Heritage Harbor.
Repairs to the line were completed last week, said Tom Wetor, Wrangell’s public works director. A dive contractor reconnected the two pieces of pipe, and borough workers then restored full service through the line instead of letting treated wastewater spill onto the beach.
“We are officially dumping sewage back in the ocean,” Wetor said March 20. He expects the beach at City Park will be reopened to the public in early April after tests are conducted at the beach to ensure no pollution is present.
Wrangell’s discharge line extends more than twice as far into the water — almost 1,800 feet — and into water twice as deep — 125 feet — as Petersburg’s setup.
Petersburg discovered its broken line while working to renew its state and federal discharge permit. After unsuccessful attempts to locate the problem using their own remotely operated underwater vehicle, the borough hired a sea cucumber diver with better equipment to inspect the diffuser at the end of the pipe.
The diffuser, installed approximately 50 years ago, was designed to spread out the discharge of treated wastewater through multiple ports to improve dilution. As of last week, all of the treatment plant’s discharge was flowing through a single broken joint instead of being dispersed over a larger area.
Despite the malfunction, Haley said historical water quality testing hasn’t shown significant environmental impact.
“We have been analyzing samples for fecal coliform bacteria and other pollutants from the area since the ‘80s and have not found any significant signs of impact,” Haley said.
“At this point we don’t really know what comes next,” he said. “It’s likely we will have to repair or replace the diffuser, but we are waiting to hear back from the EPA,” which works with the state to regulate discharge permits.
Temporary and permanent repairs on the Wrangell line cost about $100,000. The borough negotiated a settlement with the boat owner’s insurance company for $50,000.
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