Sewer Systems, and Lake Elwell Project Account established under subsection (b)(3), the principal and investment earnings, including interest, may only be used by the Fort Belknap Indian Community to pay the costs of activities relating to— (A) planning, studies, design, and environmental compliance of domestic water supply, and sewer collection and treatment systems, as generally described in the document of Natural Resources Consulting Engineers, Inc., entitled Fort Belknap Indian Community Comprehensive Water Development Plan and dated February 2019, including the Lake Elwell Project water delivery to the southern part of the Reservation