The cost per acre of the construction under § 139.1 is, therefore, calculated at $57.8782 for “A” lands and $83.9337 for “B” lands in non-Indian ownership as established by Designation Report dated August 1962. Under the provisions of the acts cited in § 139.1 the annual per acre assessment for forty equal annual payments, is hereby fixed at $1.45 per acre for “A” lands and $2.10 per acre for “B” lands for the year 1962 and each succeeding year, until the entire cost for each tract shall have been repaid to the U.S. Treasury. On those tracts where payments have been made pursuant to uncodified special regulations, annual assessments beginning with the year 1962 at the rate of $1.45 per acre for “A” lands and $2.10 per acre for “B” lands will be made until the entire cost of $57.8782 per acre for “A” lands and $83.9337 per acre for “B” lands shall have been repaid to the U.S. Treasury. Landowners may pay at any time the total of the then remaining indebtedness. Under the act of March 10, 1928 (45 Stat. 210), the unpaid charges stand as a lien against the lands until paid.