to reflect changes in construction cost indices since May 1, 2011, that are applicable to the types of construction involved in the mitigation activities that will be implemented for the Milk River Project. (g) Federal contribution to the Milk River project mitigation (1) State trust account The Secretary shall establish a trust account for the State, consisting of such amounts as are made available by the Secretary to carry out the mitigation and watershed improvement activities described in the Compact. (2) Transfer Not later than 60 days after the date on which an amount is appropriated under paragraph (4) for a fiscal year, the Secretary shall transfer the amount, at no charge to the State, to the State trust account established under paragraph (1). (3) Allocations (A) Interest The State may expend the interest accruing on amounts in the State trust account under paragraph (1) as the State determines to be appropriate to fulfill the purposes of the Compact. (B) Principal The State shall not expend the principal amount in the State trust account until— (i) the Fort Belknap Indian Community has developed, or is in the process of developing, the Tribal water rights in accordance with the Compact and this Act