The borough hopes to learn this week the exact location and condition of the kinked blockage in the treatment plant outfall pipeline that has forced a temporary solution — discharging the wastewater on the beach near City Park.
“It’s essentially been bent in half,” Public Works Director Tom Wetor said of the 12-inch-diameter plastic pipe, which was hooked Aug. 30 by a boat anchor and damaged as the anchor line was being pulled up.
Repairs could take a couple of months, he said Sept. 6. It just depends on how much work is needed.
The borough has been in contact with the boat owner and insurer.
Officials think the bent pipe is about 300 feet toward shore from the end of the line, which extends 1,800 feet out from the beach. The end of the pipe is in 120 feet of water, with a diffuser at the end to disperse the wastewater as it flows out, Wetor said. One of the unknowns is whether the diffuser was damaged in the accident.
If the bend in the line is in deep enough water to provide sufficient dilution of the wastewater to meet federal standards, the borough could cut the line there, attach a diffuser and put the outfall back into service, he explained.
There is no one in town able to dive in 120 feet of water to inspect and repair the damage, Wetor said, though a local drone operator was able to take an underwater “fly by” — but officials really need a drone that can hover and move around the damage for a closer look.
In a coincidental bit of fortunate timing, a contractor was scheduled to arrive in Wrangell this week to clean the holding tanks and inspect the community’s wastewater treatment plant. The contractor was going to bring along its underwater drone, which should be able to get better images of the damage.
“We want to see it,” Wetor said.
After they know more, the borough can talk with engineers and the Environmental Protection Agency, which regulates water quality, and come up with a repair plan. There is a Ketchikan company that could make the deep-water dive, he said.
The buried pipe is ductile iron on its run from the treatment plant and across the beach and tidelands, and then is high-density plastic pipe sitting on the seafloor out to the discharge point.
The borough has kept the EPA and the Alaska Department of Environmental Conservation informed of the situation, including the temporary solution on Aug. 30 of cutting the outfall pipe at the beach and discharging the wastewater there.
Without opening up an exit point, the kinked line was causing wastewater to back up in the treatment plant. The fastest solution was to cut the pipe where it was immediately accessible, which is on the beach.
The effluent coming out of the line has been treated at the plant — all solids are removed — and the high tide washes over the area.
“You would have a hard time knowing” anything is different on the beach, Wetor said.
Rather than take any risk with public health, however, the borough has closed off the beach, advising the public to refrain from shellfish harvesting, swimming and other recreational activities in the closed area.
The treatment plant discharges about 300,000 to 500,000 gallons of water a day, more during heavy rains when runoff and storm water drainage adds substantial volumes.
The outlet pipe is marked on marine charts, Wetor said, though the borough will consider whether buoys are an option to help prevent a similar boat anchor incident in the future.
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