United States Department of the Army, Corps of Engineers, U.S. Army Engineer Research Development Center, Vicksburg, Mississippi (Agency/Petitioner) and American Federation of Government Employees, Local 3310, AFL-CIO (Labor Organization/Incumbent Intervenor) and National Federation of Federal Employees, Federal District 1, Iamaw, AFL-CIO (Labor Organization/Incumbent Intervenor) and International Federation of Professional and Technical Engineers, Local 4, Chapter 1, AFL-CIO, Clc (Labor Organization/Incumbent Intervenor) and International Federation of Professional and Technical Engineers, Local 1017, AFL-CIO, Clc (Labor Organization/Incumbent Intervenor)