With respect to the $100,000,000 authorized to be appropriated in the Reclamation Safety of Dams Act of 1978 [
43 U.S.C.
509], costs heretofore or hereafter incurred in the modification of structures under this subchapter, the cause of which results from new hydrologic or seismic data or changes in state-of-the-art criteria deemed necessary for safety purposes shall be nonreimbursable and nonreturnable under the Federal Reclamation law.