An ethanol plant in south-central Minnesota has been nicked with a fine for polluting for the fourth time since 2009, with the latest violations involving improper venting, excessive noise levels among the missteps.

Corn Plus of Winnebago has been fined $25,141 by the Minnesota Pollution Control Agency (MPCA), the agency said Wednesday, adding that the company has begun acting to prevent future violations.

This fine comes as Corn Plus has an application pending with the MPCA to renew its environmental permits.

"The company must submit more information for that application to move forward," the agency said in a statement.

Corn Plus officials could not be reached Thursday for comment. The agreement was signed by Bill Drager, president of the Corn Plus board of directors, and the agency. The agreement is a regulatory tool used to achieve compliance with environmental laws.

In 2011, Corn Plus pleaded guilty to a federal felony charge of falsifying air pollution-monitoring data. It paid a $450,000 criminal fine levied by a federal judge and a separate $310,000 civil penalty imposed by the MPCA.

In 2010, Corn Plus paid a $200,000 fine to the state for water quality violations and agreed to environmental projects at the plant costing more than $690,000.

In 2009, Corn Plus paid a $150,000 penalty as part of a settlement with the U.S. Environmental Protection Agency for criminal charges related to water quality violations.

In this latest misstep, state inspections in 2012 and 2014, along with a file review this year, found several violations:

• Venting pollutants into the air for longer than allowed.

• Failing to inspect equipment and keep proper records.

• Failing to adjust equipment to ensure operation to control pollutants.

• Replacing equipment without permits.

• Allowing nighttime noise levels above state standards.

Corn Plus is permitted to produce 49 million gallons of ethanol annually.

Paul Walsh • 612-673-4482