A more than 30-year-old pipe that all of Bend’s sewage passes through will be essentially replaced by the end of the year — without the city needing to dig many holes or stop sewer access at any point.
The city plans to reinforce the 5-mile plant interceptor, which runs northeast from Pine Nursery Park along the canal road to Bend’s wastewater treatment plant, with a new lining forced into the pipe through manholes and cured by heat or ultraviolet light. Construction is expected to run from May to December, project engineer Jason Suhr said.
“It’s way faster than doing an excavation,” Suhr said.
All sewage in the city eventually ends up in the plant interceptor, a reinforced concrete pipe built in the early 1980s. Over time, sewer gases have deteriorated the pipe, which ranges in diameter from 30 inches to 42 inches. If the city doesn’t fix it, the pipe will eventually fail and release raw sewage into the ground — a threat to both public health and the environment. A $10 million repair will extend the pipe’s life by at least 50 years, Suhr said.
At this time, the pipeline is large enough to handle all sewage in the city and in the more than 2,300 acres Bend can annex in the coming years and won’t need to be replaced, he said.
“We’re not looking to expand the capacity,” Suhr said. “We’re looking to rehabilitate what we have.”
Contractors will force a resin-saturated wet tube into the pipe through each of the more than 40 manholes along the pipeline. Once the liner is in place, they’ll use water or air to inflate the tube to fit the existing pipe.
The tubes then are hardened with either heat or ultraviolet light. Companies specialize in one or the other, and the city will accept bids for both, Suhr said.
If heat is used, hot water or steam will be pushed through the pipe to cause the resin to harden. Otherwise, a light train — a wheeled robotic vehicle that emits ultraviolet light — can be run through the new pipe to cure it.
Each section will be patched together once the pipe is hardened and in place. Once it’s complete, the new lining will function as the new sewer pipe and it won’t matter if the existing concrete pipe continues to deteriorate.
“Once it’s in there you don’t need the concrete pipe,” Suhr said.
While repairing each section of the pipe, the city will connect temporary bypass lines to continue moving sewage to the wastewater treatment plant. These bypass pipes will lay at ground level for most sections, but they’ll need to be placed underground where the pipeline intersects with Hamehook and Deschutes Market roads.
Bids for the project will open in March and a contractor will be selected in April.
Funding will come from the city’s wastewater utility and a low-interest loan from the Oregon Department of Environmental Quality.
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