No. 91-1456. Argued September 11, 1992. Decided December 11, 1992. Thomas P. Burke, with whom Jamie L. Johnson was on the brief, for petitioner. Michael J. Gan, Atty., N.L.R.B. ("NLRB"), with whom Jerry M. Hunter, Gen. Counsel, Aileen A. Armstrong, Deputy Associate Gen. Counsel, and Paul J. Spielberg, Deputy Asst. Gen. Counsel, NLRB, were on the brief, for respondent. Ellen Greenstone, David S. Barr, and David Jonathan Cohen were on the brief, for intervenor. Petition for Review of an Order of the