Ameren Illinois is beginning to replace miles of decades-old pipes between Jefferson and southern Marion County. Starting in mid-April, the company will upgrade 15 miles of 6-inch natural gas transmission pipelines, which was placed in the 1950s between Centralia and Mt. Vernon. According to Ameren Illinois, crews will upgrade the pipeline to 10-inch steel, for the 13.75-miles, while 1.5 miles will have 8-inch steel. This is one of the longest and largest natural gas upgrades that Ameren Illinois has performed in several decades.