Unusual process conditions lead to a sewage overflow that was frozen, but recaptured before it affected the environment, according to Superior Wastewater Treatment Plant staff.

The overflow occurred Dec. 30 at a wastewater treatment process tank at the city's main treatment facility at 51 E. First St.

Process conditions resulted in foam being produced in a concrete tank, and the buildup ran down the west side of the tank.

An estimated 50 gallons of wastewater escaped the tank and froze on contact with the ground. It was subsequently collected by plant personnel and returned to the treatment process.

No wastewater or affected material left the plant as a result of the overflow, according to Jon Shamla, wastewater and treatment operations manager. He said the area where the overflow occurred is an easier area to clean up and overflows would normally wash into another process tank.

The overflow was reported to the Wisconsin Department of Natural Resources as required by law.