The owners of a defunct biogas plant in northeast Nebraska have agreed to pay a $1.1 million fine to the state and federal governments for repeated violations of environmental rules.

Big Ox Energy and its owners agreed to pay the fine as part of a settlement with regulators. The company and its insurers previously agreed to be part of a separate $1.75 million settlement with homeowners who accused the plant of sending rancid fumes through the city sewer system and ruining their homes. The plant began operations in September 2016, separating solids from industry wastewater to create methane. The plant sold the methane and injected it into a nearby natural gas pipeline. Big Ox was subject to odor complaints soon after it began operations and was cited for numerous environmental violations until it shut down in 2019.

“The Big Ox facility’s operations presented a significant risk to their workers and nearby property owners,” acting regional EPA Administrator Edward H. Chu said.

The EPA said that some of the liquid wastewater went over the sides of the facility’s roof and onto the ground at least 16 times between 2017 and 2019. On one occasion in 2018, a malfunction at the plant resulted in 80,000 gallons of liquid wastewater overflowing from its equipment.

At times the plant was also discharging methane at levels that could be flammable and hydrogen sulfide in amounts that could cause injury or death if it was inhaled.