Upon his determination that the property, or any portion thereof, has ceased to be used in accordance with the applicable terms and conditions, the Secretary may terminate a right of use and occupancy. Nonpayment of property taxes, validly assessed, on any retained right of use and occupancy shall also be grounds for termination of such right by the Secretary. In the event the Secretary terminates a right of use and occupancy under this subsection he shall pay to the owners of the retained right so terminated an amount equal to the fair market value of the portion of said right which remained unexpired on the date of termination. With respect to any right of use and occupancy in existence on the effective date of this sentence, standards for retention of such rights in effect at the time such rights were reserved shall constitute the terms and conditions referred to in section 460u–3 of this title.
With respect to improved properties acquired prior to December 28, 1980, and upon which a valid existing right of use and occupancy has been reserved for a term of not more than twenty years, the Secretary may, in his discretion, extend the term of such retained right for a period of not more than nine years upon receipt of payment prior to September 30, 1983, from the holder of the retained right. The amount of such payment shall be equivalent to the amount discounted from the purchase price paid by the Secretary for the identical period of time under the terms of the original sale adjusted by a general index adopted by the Secretary reflecting overall value trends within Indiana Dunes National Park between the time of the original sale and the time of the retained right of extension offered by this subsection.