; and (B) as may be required by reason of changes since June 2014 in construction costs, as indicated by engineering cost indices applicable to the types of construction involved. (3) Use In addition to the uses authorized under paragraph (1), amounts made available under that paragraph may be used for the conduct of related activities, to comply with Federal environmental laws, or may be transferred to the Navajo OM&R Trust Account as provided in subsection (f)(3) of section 6. (b) Navajo OM&R trust account (1) Authorization of appropriations For the purpose of assisting the Navajo Nation with the expenses of operating, maintaining, and replacing the Navajo water development projects authorized to be constructed in section 6 and described as water supply systems and water distribution systems in the agreement, there is authorized to be appropriated $11,100,000 to be deposited in the Navajo OM&R trust account established pursuant to subsection (k) of section 6, which funds shall be retained until expended. (2) Management of account The Secretary shall manage the account in accordance with the American Indian Trust Fund Management Reform Act of 1994 ( 25 U.S.C. 4001 et seq.), and shall invest amounts deposited in the account in accordance with that Act and— (A) the Act of April 1, 1880 ( 25 U.S.C. 161 )