22An employee organization that is served with a notice of application or that claims to represent any of the employees who may be affected by the application shall file its intervention, if any, in quadruplicate in Form R-6 of Schedule A not later than ten days after receipt of the notice of application, and, if it fails to file an intervention, it may be deemed by the Board to have abandoned any claim to represent any of the employees who may be affected by the application.