(a) After reviewing all information regarding the proposed undertaking and after any on-site inspection or public hearings, the agency and the commissioner shall determine if there are feasible and prudent alternatives which would avoid or mitigate any adverse impact of the undertaking on eligible or registered property.

(b) If the commissioner and the agency agree on a course of action which would avoid or satisfactorily mitigate an adverse impact, their agreement shall be embodied in a Letter of Resolution, executed by both parties, and specifying how the undertaking will proceed. Except for submission of the certification of completion described in subdivision (c) of this section execution of a Letter of Resolution will conclude the consultation process.

(c) At the conclusion of the undertaking the agency shall certify in writing that the undertaking has been completed in accordance with a Letter of Resolution. The commissioner may request drawings, photographs or other materials to document satisfactory completion of the undertaking.

(d) If the agency determines that there are no feasible and prudent alternatives which would avoid or satisfactorily mitigate adverse impacts and also determines that it is nevertheless in the public interest to proceed with the undertaking, it may unilaterally terminate consultation by declaring that no feasible and prudent alternative exists. The agency must give the commissioner written notice of this determination which shall include the reasons for the agency's decision and the facts supporting it.

(e) The agency and the commissioner may agree that there are no feasible and prudent alternatives which would avoid or mitigate adverse impacts but that it is nonetheless in the public interest to proceed with the undertaking. In such event, the agency and the commissioner shall make a joint written declaration to this effect which shall include the factual basis for their decision.