Broken Nashua pipe is leaking sewage into Cedar River

A broken sewer pipe in northern Iowa’s Nashua has been leaking up to 16,000 gallons of wastewater per day into the Cedar River for an unknown amount of time, according to the Iowa Department of Natural Resources.

The leak was discovered Wednesday night after a passerby reported that part of the river's surface appeared to be bubbling periodically near the Iowa Highway 346 bridge.

City employees determined the disturbances coincide with the activation of a pump that pushes wastewater through a 6-inch pipe toward the city's treatment plant. The pipe was buried under the river about a century ago and carries about 10 percent of the city's total wastewater, said Nick Henningsen, Nashua's sewer operator.

He suspects the pipe failure might be related to bridge work about three weeks ago. A company was hired by the state to reinforce the bridge's support pillars with rock, and excavation that was part of that work damaged an electrical line. It's possible the excavation also damaged the sewer line, Henningsen said.

Work to repair the pipe is expected to conclude Friday. Nashua has hired a company that plans to cover the pipe with sand and other material to build a peninsula over the broken area, and then dig down into it to reach the pipe and keep river water out, Henningsen said.

There are no obvious environmental effects from the leak, said Andrea Errthum, an environmental specialist for the Iowa DNR who investigated. There were no dead fish and the river wasn't discolored.

The rate of the leak is relatively trivial compared with the flow of the river, according to U.S. Geological Survey data. Downstream at Waverly, the river is flowing more than 400 million gallons of water per day.

The city is warning residents to avoid that area of the river until repairs are complete. Tests for bacteria contamination are pending.

Waverly and other cities downstream from the leak do not draw drinking water from the river itself, Iowa DNR data show. Nashua is about 75 miles northwest of Cedar Rapids.

Comments: (319) 368-8541; jared.strong@thegazette.com