Any Pleading may be amended without leave until thirty (30) days prior to the hearing. Any Pleading may be amended at any time until three (3) business days prior to the hearing, provided that it does not act as a surprise to any other Party. Any amendment to a Pleading which operates as a surprise to any other Party may be granted only upon written motion showing good cause and that no harm will result.
34 Tex. Admin. Code § 67.33