No. 80-1865. Submitted June 17, 1981. Decided June 24, 1981. Linda B. Weisel, Washington, D.C., for petitioner. Nicholas R. Fiorella, Springfield, Mo., for respondent Clayton Const. Corp. Petition from the National Labor Relations Board. Before McMILLIAN and ARNOLD, Circuit Judges, and HANSON, Senior District Judge. The Honorable William C. Hanson, United States Senior District Judge for the Northern and Southern Districts of Iowa, sitting by designation. PER CURIAM. The National Labor Relations