A water utility is expanding its corporate office in southwestern Illinois.  Illinois American Water says the $1.4 million project at its Belleville location includes a 5,200-square-foot building that will provide more office and storage space.  The Belleville News-Democrat reports construction is expected to be completed this fall.  The investor-owned utility provides water and wastewater treatment services for 1.2 million people in 127 communities.  It also operates a customer service center in Alton and a quality control and research laboratory in Belleville.