 Because of these objections , United States Secretary of the Interior Stewart Udall formally opposed construction of the dam in 1967 , and the project was shelved . The U.S. Army Corps of Engineers nevertheless completed its engineering study of the project in 1971 , and the final report was released to the public in 1979 . In 1980 , U.S. President Jimmy Carter created the Yukon Flats National Wildlife Sanctuary , which formally protected the area from development and disallowed any similar project . 
