The passage of the 1975 Act re-drawing the GCNP boundary launched four studies.
The first, to check whether the northern areas incorporated from the Monument were suitable for Park status, had been completed by NPS within the year and found the lands belonged in the Park. End of story. Well, except that I learned through talks with NPS officials that BLM had objected to being considered part of the recommendation, so some language had to be adjusted. There was also a bit of a flap over the cost.
The second, of Wilderness, covered in my book on river management, Hijacking A River, but not in this blog, was completed by NPS within the mandated period, and a near-perfect recommendation sent to the President, at which point the commercial motorboat operators and their allies prevented the recommendation from being sent to Congress. 1980 brought the Reagan administration that deep-sixed the wilderness proposal. Not quite the end of the story; the recommendation remains viable, awaiting a change in the political environment.
The fourth study, the Secretarial Land Use Plan for the lands added to the Havasupai Reservation, was under the jurisdiction of the Havasupai themselves and the Bureau of Indian Affairs. It took several years. I will deal with it later.
The third study was not set up in as clear-cut a manner as the others. First, it was not mentioned in the legislation itself, but was instead ordered by the conference that resolved differences between the House and Senate. Not even really a compromise, it was what Representative Udall could salvage from the opposition to actually adding to the Park certain prime pieces of the Canyon's north side. Second, the areas involved were not officially designated, though named in the Conference's report, and they had been included in the map approved by the House. Third, the Interior Secretary was directed to do a study and send the recommendations to Congress, but without any sort of due date. What was clear was the instruction "to study these areas to determine if they, or any part of them, qualify for national park designation" and report those findings to Congress.