As used in this part, the following terms have the specified meanings:

Unwarranted failure to comply means the failure of a permittee to prevent the occurrence of any violation of his or her permit or any requirement of the Act due to indifference, lack of diligence, or lack of reasonable care, or the failure to abate any violation of such permit of the Act due to indifference, lack of diligence, or lack of reasonable care.