The Corporation is authorized and directed to construct, in United States territory, deep-water navigation works substantially in accordance with the “Controlled single stage project, 238–242” (with a controlling depth of twenty-seven feet in channels and canals and locks at least eight hundred feet long, eighty feet wide, and thirty feet over the sills), designated as “works solely for navigation” in the joint report dated January 3, 1941, of the Canadian Temporary Great Lakes-Saint Lawrence Basin Committee and the United States Saint Lawrence Advisory Committee, in the International Rapids section of the Saint Lawrence River together with necessary dredging in the Thousand Islands section; and to operate and maintain such works in coordination with the Saint Lawrence Seaway Authority of Canada, created by chapter 24 of the acts of the fifth session of the Twenty-first Parliament of Canada 15–16, George VI (assented to December 21, 1951): Provided, That the Corporation shall not proceed with the aforesaid construction unless and until—