After nearly two years of planning, Utah's largest electric utility announced Tuesday that crews had begun constructing a $600 million, 135-mile high-voltage transmission line from a new substation near Downey, Idaho, to an existing substation near the Salt Lake City International Airport. Rocky Mountain Power spokesman David Eskelsen told the Deseret News that work on the Populus to Terminal transmission line is under way, with the first segment in PacifiCorp's Energy Gateway transmission expansion scheduled for completion in 2010.