Whenever more than one Federal agency is involved in a Federal agency activity or its associated facilities affecting any coastal use or resource, or is involved in a group of Federal agency activities related to each other because of their geographic proximity, the Federal agencies may prepare one consistency determination for all the federal activities involved. In such cases, Federal agencies should consider joint preparation or lead agency development of the consistency determination. In either case, the consistency determination shall be transmitted to the State agency at least 90 days before final decisions are taken by any of the participating agencies and shall comply with the requirements of § 930.39.