Approximately 500,000 gallons of untreated wastewater was intermittently discharged over a 25-hour period on Madison's north side last week, according to a release.
The Madison Metropolitan Sewerage District said during the relining of one of its interceptor sewers near Golf Parkway, officials said.
During the relining, untreated wastewater was diverted around the relining area, according to the release. MMSD's contractor had three pumps on site to divert the wastewater, which included two back-up pumps.
On Nov. 16, the primary pump and the two backup pumps failed, officials said. When the pumps failed, a temporary discharge of wastewater went to nearby low-lying areas and ditches.
The Wisconsin Department of Natural Resources was notified of the spill, according to the release.
Officials said the pump failure has been corrected, and appropriate remedial actions have been taken.