(b) The running of the one-year limitation period is suspended during the time a potential charging party and respondent are voluntarily engaged in a dispute resolution process involving a claim of unlawful discrimination under this chapter, including arbitration, conciliation, mediation or grievance procedures pursuant to a collective bargaining agreement or statutory, charter, ordinance provisions for a civil service or other employment system or a school board sexual harassment or sexual violence policy. A potential respondent who participates in such a process with a potential charging party before a charge is filed or a civil action is brought shall notify the department and the charging party in writing of the participation in the process and the date the process commenced and shall also notify the department and the charging party of the ending date of the process. A respondent who fails to provide this notification is barred from raising the defense that the statute of limitations has run unless one year plus a period of time equal to the suspension period has passed.