Baetjer v. United States , 143 F.2d 391 at 396-97 (1st Cir. 1944); accord Int’l Paper Co. v. United States , 227 F.2d 201 (5th Cir. 1955); Porrata v. United States , 158 F.2d 788, 790 (1st Cir. 1947) (“Certainly one of the elements which would be considered by the mythical ‘willing buyer’ of the [remainder property] would be the availability of a suitable substitute . . . to take the place of the one formerly on [the part taken].”); see Ga.-Pac. Corp. v. United States , 640 F.2d 328, 359 (Ct. Cl. 1980) (per curiam) (burden to show that “replacement old-growth timber was not available, or if available, at least, the burden to show persuasively that under existing circumstances it would be economically unfeasible