(a) In the event of consent to an assessment by the person concerned, or if, upon the record made at an administrative hearing, the Board finds that the grounds for having assessed the penalty have been established, the Board may issue a final order of assessment of civil penalty. In its final order, the Board may modify the amount of the penalty specified in the notice of assessment.

(b) An assessment order is effective immediately upon issuance, or upon such other date as may be specified therein, and shall remain effective and enforceable until it is stayed, modified, terminated, or set aside by action of the Board or a reviewing court.