43 C.F.R. § 2522.3
Under the provisions of the Act of March 28, 1908 (35 Stat. 52; 43 U.S.C. 333 ), the period of 4 years may be extended, in the discretion of the authorized officer, for an additional period not exceeding 3 years, if, by reason of some unavoidable delay in the construction of the irrigating works intended to convey water to the land, the entryman is unable to make proof of reclamation and cultivation required within the 4 years. This does not mean that the period within which proof may be made will be extended as a matter of course for 3 years. Applications for extension under said act will not be granted unless it be clearly shown that the failure to reclaim and cultivate the land within the regular period of 4 years was due to no fault on the part of the entryman but to some unavoidable delay in the construction of the irrigation works for which he was not responsible and could not have readily foreseen (37 L.D. 332). It must also appear that he has complied with the law as to annual expenditures and proof thereof.
43 C.F.R. §2522.3