After a company twice contaminated the water system at Normandale Community College last year, its owner can no longer do plumbing work in Minnesota, the state Department of Labor and Industry said last month.

Employees of Mechanical Solutions, Inc., a St. Paul company owned by Richard Ellingsworth Jr., were working on a cooling tower at the Bloomington college in June 2009. They attached a hose without using a backflow preventer, allowing ethylene glycol into the drinking water system. Seventeen days later, company workers let chemicals backflow into a water heater. No one got sick. Both times the system was flushed. A $25,000 fine against Ellingsworth was vacated after the department was told the business had been closed.