* Robert D. Stevens has joined Centennial...

* Robert D. Stevens has joined Centennial Civil Engineers, Inc. in Irvine as vice president and regional manager. Previously, he was vice president and office manager of Parsons, De Leuw, Inc. in Tustin. In addition, Six C. Silva has been appointed director of business development. He formerly held marketing positions with Holmes & Narver, Inc. and Greiner, Inc. in Orange County. Centennial, which specializes in transportation planning, engineering and construction-management services for highways, rail and airports, is a subsidiary of Morrison Knudsen Corp. in Boise, Idaho.