Cedar Rapids makes $5 million emergency repairs on large pipe at Water Pollution Control Facility

CEDAR RAPIDS — The city of Cedar Rapids has made emergency repairs that will cost an estimated $5 million on an 84-inch concrete pipe within the Water Pollution Control Facility.

Utilities Director Roy Hesemann said this is an internal pipe to the facility near Bertram. During the treatment process, flow from the waste stream comes in a larger 96-inch pipe to the facility’s main lift, which pumps it back up to the surface and through a metering structure. That’s where the 84-inch pipe starts.

This pipe, which needed repairs, takes the waste stream from its initial point of treatment through roughing filters — domed structures with arms that rotate inside and distribute wastewater to go through a treatment process that reduces organic matter.

A structure in between the pipes provides water to roughing filters. Then it recirculates and material is conveyed to the next section and splits off into a secondary treatment process.

Corrosion caused sinkhole on pipe

Staff noticed a sinkhole on the large pipe in late January or early February, Hesemann said. Upon investigation, staff found the inner part of the pipe was highly corroded and had fallen in, which is what he said caused the sinkhole.

The pipe corrosion was caused by long-term exposure to corrosive hydrogen sulfide gases, according to city council documents.

“That’s the only pipe to convey that wastewater stream through that section of the plant, so we needed to do something very quickly in order to replace that pipe and make sure that we had full pipe capacity should we get any storm events and higher flows and anything that would create more harm than damage,” Hesemann said.

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Crews began work to replace the pipe last week and wanted to move quickly because of the potential for storms, Hesemann said. It was deemed an emergency because of the pipe’s critical nature, so staff moved quickly to bring in bypass pumps that could pump around a 900-foot long section.

The contractor excavated out the old pipe and replaced it with a new concrete pipe with high-density polyethylene liner, Hesemann said, so there is “much more length of time before anything starts to decay.”

The pipe is now installed, but Hesemann said there will be some restoration and ancillary projects associated with it and restoration of the underground area.

The pipe repair — estimated to cost $5 million — was funded with wastewater department reserves.

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