Dist. Ct. did not err in granting defendant-union’s motion for summary judgment in plaintiff-employer’s action seeking to vacate arbitration award in which joint arbitration committee (JAC) upheld union’s grievance that challenged plaintiff’s creation of two new companies that used non-union workers and competed for projects, where customers wanted lower costs associated with use of non-union workers. JAC found that defendant and non-union companies were essentially “single employer” due to plaintiff’s control over non-union companies, such that defendant owed non-union workers in new companies union wages pursuant to collective bargaining agreement, and union was owed union dues for said workers. Moreover, Dist. Ct. could properly find that single employer issue was question of contract that was within JAC’s authority to decide. Also, defendant waived argument that instant dispute was not arbitrable because there had been no threshold finding by NLRB that instant non-union workers were within same bargaining unit as defendant’s union workers, where plaintiff had failed to raise said issue with JAC.