(a) Within 15 days of receipt of an agency determination concerning a State agency project (except those pursuant to section 579.3[d][3] of this Part), the State agency shall make one of the following responses to the agency, in writing:

1. (1) if the agency determined that the project will not be inconsistent with the plan and will not have an undue adverse impact upon the resources of the park, the State agency shall report that it will undertake the project in accordance with the findings of fact of the agency decision;
2. (2) if the agency determined that the project will not be inconsistent with the plan and will not have an undue adverse impact, provided certain conditions are met, the State agency (i) shall report that it will comply with the conditions, or (ii) if it proposes not to comply with the conditions, shall fully explain and justify why it will not comply;
3. (3) if the agency determined that the project will be inconsistent with the plan or will have an undue adverse impact, the State agency (i) shall report that it will not undertake the project, or (ii) if it proposes to undertake the project, shall fully explain and justify such decision and describe the measures it will take to mitigate the inconsistency or adverse impacts.